Rescue operations are captivating many Chinese social media users, who are actively sharing state media coverage of the situation in northern Thailand.

"Watching this from Shanghai and only hoping for the best for these poor boys. I can't imagine how badly they must want to see daylight again," wrote one user on the popular Sina Weibo microblogging site. "When the story first emerged, I actually did not realise it was taking place in Thailand. I mistook it as a national story and I think this type of tragedy could happen in any country. Let's all hope for the best outcome and that these lives will be saved," wrote another Weibo user.

Heavy rain was falling earlier on Sunday, but the weather has cleared now, correspondents say.

The rescue operation has been continuing for a number of hours now.

The first of the trapped boys is expected to come out of the cave by about 21:00 local time (14:00 GMT).

It's worth remembering that the boys have no diving experience - and some of them cannot even swim.

So far, there have been no official updates about the progress of the risky operation.

The BBC's Sophie Long reports on why the rescue operation was launched earlier on Sunday, and how the Thai authorities are planning to execute the risky plan.

Image source, Reuters

As the rescue operation began, children across Thailand have been praying for the safe return of the trapped boys and their coach.

Thailand's government has released details about the rescue plan.

"The government has distributed a GFX about how the boys will dive out from Tham Luang cave:

• equipment - air tanks, full face masks

• two divers accompanying one child

• they dive together, guided by the rope placed by the rescuers

• when facing a very narrow path, they will release the tank from the back and slowly roll the tank and guide the kid through the channel

• from Chamber 3 to the cave's mouth they will walk

The government says the advantages are that this could be done fast and without using much resources.

But it also warns that this requires requires high-level skills of the divers; the boys should have some diving skills, strong mind and should not be panicking.

Meanwhile, it is raining heavily in the area, the BBC's Helier Cheung reports.

The authorities say a forecast of bad weather was a key factor in launching the operation.

The Thai Navy SEAL Facebook page has posted this image of divers clasping hands before the rescue attempt, with the message: "We - Thai and the international teams join forces to bring the young Wild Boars home."

Image source, EPA/ROYAL THAI NAVY

The boys trapped in the cave will be divided into four groups, the Bangkok Post is quoting a source as saying.

It says the first group will have four people, while the second, third and fourth will have three people. The coach will be in the last group.

People across Thailand are flocking to help rescue operations in the little ways they can - whether they're cooking a meal for those in Tham Luang, or cleaning the uniforms of rescue workers:

That's how long it will take for divers to make a return trip - six hours into the cave, and five hours out.

Medical personnel, relatives, rescue workers and journalists are just some of many people who have set up base at the rescue camp these past few days.

People have now been moved to make way for rescuers to head into the cave, but here's how it looked before things got underway today:

The rain and the heavy traffic around the cave and the media centre have made it tough going for those on the ground, as our colleague shows.

Former cave diver and rescuer Geoff Crossley described the challenges facing the rescue operation to BBC Radio 5 Live.

"It’s going to be an extremely difficult task to get them out. A friend of mine in cave diving would say there’s two speeds in cave diving, which are dead slow and stop, which is why it’s going to take some time," he said.

Mr Crossley said he was involved in a similar, smaller-scale rescue in flooded caves in Yorkshire.

"Visibility is one of the worst issues you find with cave diving. Silt, mud gets stirred up by people going through and also by what’s actually in the water coming in, if it’s flood water," he said.

"If you can’t see very far in front of your face at all, that makes it very difficult, because there could be rock projections which could catch on equipment hoses etc."

Keeping the children calm during the rescue will be essential, Mr Crossley said.

"I can only hope that the children might see it as perhaps a challenging adventure," he said.

"When we carried out our rescue, one of the accompanying divers swam backwards and kept eye contact with the non-diver all the time and fed the guideline to the non-diver all the time and made sure they got an instant reaction if there was likely to be any panic."

Thailand's Prime Minister Prayuth Chan-ocha will fly to Chiang Rai on Monday afternoon local time, the Bangkok Post is quoting government sources as saying.

The boys will be evacuated one-by-one over two or three days, the rescue centre is quoted as saying by the AFP news agency.

If you're just waking up to this extraordinary story now, here's what you need to know:

- 12 boys and their football coach have been trapped in a cave for more than two weeks. They first entered on 23 June.

- They were found by two British rescue divers some five days ago - but they've remained trapped there since as conditions had not been favourable to get them out.

- But a rescue mission to get them out is now under way. More than 1,000 people from around the globe have been involved in this massive effort.

- The first boy is expected to make his way out by 21:00 local time (14:00 GMT)

Some 128 million litres of water has been pumped out of the cave over the past few days - rescuers were literally working around the clock to drain water out.

The water level in the cave is now said to be ideal for getting the boys out of the cave.

Image source, Getty Images