Trump's just tweeted a vague claim about people trying "to STEAL the election". He didn't offer evidence, but said "votes cannot be cast after the polls are closed".

But this year there are some changes to state rules because of the pandemic - and counts, in general, will take longer because more people sent their votes in by mail.

Numerous national and state-level studies have shown that although there have been isolated cases, electoral fraud is very rare.

Our Reality Check team has looked into these questions of voter fraud and postal voting problems:

• 'Rigged' votes, body doubles and other false claims
• Do postal ballots lead to voting fraud?

Research from BBC Monitoring found that over 70 tweets from President Trump’s official account have cast doubt on or criticised mail-in voting, mentioned voter fraud, or referenced rigged elections.

Twitter has labelled a tweet from President Trump as possibly "misleading about an election or other civic process" and urged users to find accurate information about the election.

Trump had tweeted shortly after his rival Joe Biden took the stage in Delaware to urge patience as the vote counting process is completed.

"We are up big, but they are trying to steal the election," Trump wrote. "We will never let them do it. Votes cannot be cast after the Polls are closed."

The president has often made unsubstantiated claims about vote "stealing" during the campaign.

He also said he will be making a statement soon.

Fox News has called Arizona for Joe Biden, but the state's Republican governor, Doug Ducey, says "not so fast".

"Let's count the votes - all the votes - before making declarations," he said in a late-night tweet.

About one quarter of the state's votes are yet to be counted. In 2016, Trump won the state by just 3.5% and Democrats have been working to flip it for Biden this time around.

It looks like we'll have to wait a little longer to see what happens.

California Democrat Nancy Pelosi is singing the praises of House Democrats, who have retained their majority in the chamber.

It means Pelosi will likely return as Speaker of the House when the new Congress convenes.

The issue that helped hand Democrats the win was healthcare, Pelosi said.

Democrats still need to win four seats in the upper chamber of Congress, the Senate, to gain a majority there.

When Florida was first projected for Trump by Fox News, the mood began to change on the BBC voter panel.

One voter at a large gathering in Florida showed us a room full of Trump supporters cheering loudly for the president. Another man in Texas who backs Biden told us he hadn't been this anxious "in years and years and years".

Image source, Getty Images

"We knew this was going to go long, but who knew we would go into maybe tomorrow morning, maybe even longer!" Biden says, speaking now from Delaware.

"But we feel good about where we are. I'm here to tell you tonight we believe we're on track to win this election."

He adds: "It ain't over until every vote, every ballot is counted."

Watch his speech here...

Image source, Getty Images

To the sound of blaring car horns from his audience of supporters, Joe Biden and his wife Jill take the stage at the outdoor venue in Wilmington, Delaware.

"Good evening. Your patience is commendable," he says, adding: "We feel good about where we are."

Anthony Zurcher
BBC North America reporter

Florida has let Democrats down once again. Despite a massive effort in the state, including hundreds of millions of dollars from businessman Mike Bloomberg, Donald Trump has again won what has become his adopted home state.

He did so by once more running up good numbers in traditionally Republican areas and eating into Joe Biden’s support among Hispanic and African-American voters in the Democratic strongholds of south Florida.

With the win, Trump clears the first big hurdle standing between him and re-election – and has shown, at least in this state, that polls giving Biden an advantage are not altogether reliable.

Now Trump has to show that he still has the magic touch in the industrial Midwest states that delivered him the White House in 2016.

He also has to secure victories in places like North Carolina and Arizona, which offer Biden other promising pathways to an electoral college victory.

Florida is projected to vote for Donald Trump. It's a race we've been watching all night.

As a large battleground state, its 29 electoral votes have been decisive in previous presidential elections.

In 2000, just 537 votes in Florida delivered the White House to Republican George W Bush. The state chose Donald Trump four years ago, but voted twice for Obama.

Former Nasa astronaut Mark Kelly has just been on stage in Tucson, Arizona, declaring a victory over Republican senator and former Air Force officer Martha McSally.

"The votes are counted, and we're going to be successful in this mission," he said on stage. Fox News projected his win.

"Tonight is not about celebrating," he added. "Tonight is about getting to work."

In a message to his daughters, he said that when they were young he used to go to work blasting off into space. But this time, it's to Washington DC where he'll be journeying into the great unknown.

Kelly is a political newcomer whose wife, Gabrielle Giffords, is a former congresswoman who was shot in the head while meeting with constituents in 2011. In the years that followed, the couple became well-known for their advocacy on gun control.

No doubt you’ll have heard a lot this year about mail-in ballots.

Voting by post is not a new thing – in 2016, they made up about a quarter of all ballots cast. But it was even bigger this year, with many Americans anxious to minimise their exposure to Covid-19.

Some states started counting mail-in ballots as soon as they arrived, others at a set period before election day, while others didn’t begin counting until election day itself.

As ever it is the handful of swing states that are being the most closely scrutinised. Two key battlegrounds targeted by both Biden and Trump – Pennsylvania and Wisconsin – only started counting on election day, a process that takes longer than counting in-person votes.

Authorities in Michigan explicitly warned that it could take until Friday to tally all the votes. , externalNow Bloomberg News is reporting that final results will not come from this key state until Wednesday evening.

It could still be some time before a result is confirmed.

Image source, Reuters

Anthony Scaramucci, one of Trump's most bombastic former White House officials, has been speaking to Katty Kay and Andrew Neil on our TV election special programme.

“I think Joe Biden is gonna pull this out. He’s got Wisconsin, Michigan, Pennsylvania leaning towards him,” Scaramucci said. The former Trump ally is an outspoken critic of the president now, and didn’t hold back tonight.

Explaining Trump's better-than-expected performance in some areas, Scaramucci said: “People see Donald Trump as an avatar for their anger."

Despite that, the former official declared that Trump "blew the coronavirus pandemic."

"He trashed the economy. He’s praising despots and trashing democratic leaders across the world.”

But, Scaramucci admitted, his one-time boss always has the ability to surprise.

Democratic challenger Joe Biden is expected to give a speech from the Chase Center in downtown Wilmington, Delaware, in the coming minutes.

With results still trickling in, and several swing states still to be decided, Biden is not expected to declare victory or concede defeat.

Meanwhile, Trump is also expected to give some kind of speech tonight. He is hosting a watch party at the White House with some 400 attendees.

Anthony Zurcher
BBC North America reporter

While many of the in-play Sun Belt states – Florida, Georgia and Texas – appear to be disappointments for Joe Biden, Arizona is offering a ray of hope. The Democrat posted a substantial lead as early votes were quickly tabulated in the state, and he could be on his way to making it the first to switch sides from the 2016 results.

If Biden does prevail in the border state, his path to the presidency becomes less daunting.

Instead of having to win all three “blue wall” states (Michigan, Wisconsin and Pennsylvania) that Hillary Clinton lost, he would only have to flip two of them (plus winning an electoral college vote in Nebraska or all of Maine, if he loses Pennsylvania).

Donald Trump publicly feuded with Arizona's favourite son John McCain prior to the senator’s death in 2018, and his widow, Cindy McCain, endorsed Biden earlier this year.

Although the president held several rallies in Arizona in the past week, it appears the trends that have been moving the desert state toward the Democrats in recent years will deliver an important boost to Biden on what is shaping up to be a long night.

Key Trump ally Senator Lindsey Graham has told supporters he is going back to the Senate "with a purpose" after holding on to his seat in South Carolina.

Graham, who is chairman of the powerful Senate Judiciary committee, appeared to be in the fight of his political life against an opponent who had raised record amounts of campaign funding.

He said: "I've never wanted my job more than I do now. I've never appreciated my job more than I do now. I've never been more grateful to have it, and I've never been more prepared to do it than I am now."

His victory is a boost for Republicans looking to keep their Senate majority.

Outlining his priorities he told supporters: "We are going to put our national security interests ahead of everything else because without national security, nothing else matters."

Virginia is projected to vote for Joe Biden.

The state used to vote Republican at presidential elections, but voters have swung to the Democrats during the last three elections.

Two more projections in now. Ohio and Idaho are both predicted to go to Donald Trump.

Ohio, the Buckeye State, was a major election battleground - it has backed the winner of nearly every presidential race over the last 200 years, including Trump in 2016.

There was no surprise with Idaho, with its four electoral college votes - the state has backed Republican candidates in the last 13 presidential races.

As the polls closed, US voters have been sharing with BBC how they feel about their candidate.

One voter at a watch party was hopeful, while another said they were "very, very, very anxious".

Former Trump campaign adviser Bryan Lanza has told the BBC that the election is clearly going to be closer than many people expected.

Although the 2000 election was decided by one state - Florida - it might be decided by five states in this election, he said. "At the end of the day, we are seeing a much closer election than what the pundits and what the pollsters said we were going to have, and we shouldn't be surprised by that," Lanza added.

"It's a testament to the Trump campaign, putting away all the noise and focusing on what they knew they had to do to win."

Image source, Getty Images

The Midwestern state of Ohio – with its 18 electoral delegates - has long been a key battleground state in presidential elections.

Donald Trump won there in 2016 with a margin of over 8%, appealing to working-class voters in one of America’s industrial heartland states.

This bucked a trend of much closer election results over the years.

Ohio has backed the eventual White House winner in the last 14 elections.

Polling stations closed at 19:30ET (00:30 GMT).

The deadline for counting all absentee ballots is 13 November. However, the overall number of outstanding ballots are being reported on election night.

So far, with 89% of votes counted, Trump is at 53%, while Biden is on 45%.