We now have more on our earlier report about difficulties accessing social media sites.

A woman in Bodrum, western Turkey, has told the BBC she's facing the same problem.

"After the [attacks], the government restricted some social media apps such as X and Instagram […] and so we are using VPN applications to use these sites to get some information about what happened in Ankara,” she says.

We are still yet to hear from the Turkish government officially about any restrictions, but earlier, the Chairman of Turkey’s Radio and Television Supreme Council (RTÜK), Ebubekir Şahin, expressed his concern that "unconfirmed information" is circulating on social media.

At the scene "many people are waiting in front of the company, with the relatives of employees trying to get information about their loved ones", says one local television journalist.

Mevlut Isli tells BBC OS that it "is a major incident", with "a large number of ambulances" currently at the site.

We've received what appears to be CCTV footage of a gunman firing his weapon inside a Turkish Aerospace Industries building.

He is wearing a rucksack and armed with what appears to be an assault rifle, shooting through sliding doors at the entrance to a building in the complex. Watch below:

What happened

• Gunfire and explosions have been reported outside the Turkish Aerospace Industries (TAI) headquarters
• Turkish officials are describing this as a "terrorist attack"

Four people killed

• Four people have been killed, with 14 wounded, officials say
• Two suspects - one man and one woman - have been "neutralised," Turkey's interior minister says

What is Turkish Aerospace Industries?

• TAI is a state-owned arms and aerospace technology company in Turkey, located in Kahramankazan, about 17 miles (28km) north-west of Ankara

What we don’t know

• Who is behind the attack, although you can read analysis from Frank Gardner
• Exactly how many attackers were involved

Unclear whether suspects pictured in viral videopublished at 16:52 British Summer Time 23 October

16:52 BST 23 October

By Nick Eardley and Joshua Cheetham

When incidents like this happen, BBC Verify looks at footage being posted online to figure out what is real and build up a picture of what's happened.

There is a lot material being circulated from this attack which we're working through.

One video we have verified so far is filmed at a car park at the Turkish Aeropace Industries (TAI) building, just outside the capital Ankara.

A few seconds in, you can see and hear explosion under a distinctive part of the building – which is how we verified the location video.

Then, about 16 seconds into the video you can see what looks like a man with a large gun and a big pack moving into the shot.

He moves forward, then turns around. We can't be sure at the moment if this was one of the people responsible for the attack due to the video quality and how far away they are.

There is more dramatic footage from the complex which we're working to verify at the moment.

We've got you an update on the casualties from the attack.

Turkey's interior minister, Ali Yerlikaya, has stated that the death toll from the attack has risen to four.

Fourteen people are injured, as we've reported earlier. However, Yerlikaya also mentions that three of the injured are in a serious condition.

He adds that the two "terrorists" previously reported as "neutralised" are one female and one male.

Paul Adams
Diplomatic correspondent

It’s not clear whether the Turkish interior minister’s statement that two "terrorists" had been "neutralised" means the incident involved only two people or more than that.

Videos circulating on social media show two attackers, both carrying rucksacks and heavily armed, arriving at the gates of the facility in what appears to be a yellow taxi.

They immediately open fire on pedestrians outside the gates, before entering the building.

"I condemn this heinous attack," Ali Yelikaya says. "Our fight will continue with determination and determination until the last terrorist is neutralised."

A sudden blast is seen after a series of gunshots at the scene of the incident

Rushdi Abualouf
Reporting from Istanbul

At 17:48 Turkish time (15:48 BST), users in large areas of Turkey complained about their inability to use social media sites YouTube, Instagram, Facebook and Twitter.

More from the Turkish government.

The Ankara chief public prosecutor’s office has started a judicial investigation into the attack, according to Yılmaz Tunç, Turkey's justice minister.

He mentions in a post on X that one deputy chief public prosecutor and eight public prosecutors have been assigned to the case.

Image source, EPA

We're now starting to hear from international leaders.

Mark Rutte, Nato's secretary general, has posted on X, describing the report on the attack as "deeply concerning".

He says:

Key question is which group might be behind this attackpublished at 16:14 British Summer Time 23 October

16:14 BST 23 October

Frank Gardner
Security correspondent

Turkey is no stranger to attacks branded as terrorism.

Historically, these have mostly been blamed on Kurdish separatists, whose camps in northern Syria and elsewhere in the region have come under repeated airstrikes from the Turkish air force.

But the Islamic State group (IS) is also present in Turkey and then there is the question of the Turkish aerospace industry which produces drones that have changed the entire course of a war between Armenia and Azerbaijan.

In the early stages of Russia’s full-scale invasion of Ukraine, the latter made large use of Turkish-made Bayraktar drones to target Russian tanks before Ukraine began mass producing its own drones.

So the key question now, as the investigation into this attack gets under way, is who would benefit from doing this and why?

We can bring you CCTV images now from inside the aviation facility which appear to show a man holding a weapon.

A reminder - there are currently few confirmed details about the nature of the incident, or how many people may have been involved.

Just now, the Turkish interior minister has confirmed that three people have been killed, and he says 14 have been wounded in the incident.

In a post on X, Ali Yerlikaya says that two suspects in the attack on the Turkish Aerospace Systems headquarters have been "neutralised".

Three people have been killed in the attack on Turkish state-owned aviation company's headquarters, according to the local mayor.

Selim Çırpanoğlu, mayor of Kahramankazan province, told the Turkish TV channel Tele1 that five other people had been wounded, Reuters reports.

Turkish Aerospace Industries is a state-owned arms and aerospace technology company based near the capital Ankara.

The firm produces both military and civilian planes and helicopters, as well as drone systems for the Turkish armed forces and others worldwide.

Tai was launched, according to its website, to reduce Turkey's reliance on foreign imports of aerospace technology for military uses.

It is the company designated by the Nato member to be the licenced manufacturer for the US-designed F-16 fighter jets. Tai also plays a role in modernising older aircraft for use by the Turkish military.

The firm's two principle owners are the Turkish Armed Forces and a civilian arm of the Turkey's government charged with improving its defence capabilities and manage military procurement.

The site that has come under attack is the headquarters of TAI in Kahramankazan, around 17 miles (28km) to the north west of Ankara.

According to the aerospace company's website, the campus covers an area of about 1.5 square miles (4 sq km).

It is not yet clear exactly where or what has been attacked on the large site, we will update you when we know more.

• Gunfire and explosions have been reported outside the Turkish Aerospace Industries (TAI) headquarters near Ankara
• The company is a state-owned arms and aerospace technology company
• Turkish Interior Minister Ali Yerlikaya called it a "terrorist attack", saying people had been killed and wounded
• He said the "attack" took place at the company's facilities in Kahramankazan, located in the district of Ankara, about 25 miles outside Turkey's capital.
• Footage of the incident shown by local media initially showed large clouds of smoke and a large fire, AFP reports
• We don't yet know specifics in terms of casualty numbers or how many people may have been involved

We'll bring you more information as we get it.

We're still waiting for a clear picture of what has happened at the Turkish Aerospace Systems headquarters, where a cloud smoke can be seen rising from the facility.

Ambulances, soldiers and police have gathered at the scene following the blast and reports of gunfire.

Image source, Getty Images

Image source, Getty Images

Image source, Getty Images