SINGAPORE — Prime Minister Lee Hsien Loong has offered the Republic's assistance to help bring a youth football team trapped in a flooded cave complex to safety.

"I have written to (Thailand's) PM Prayuth Chan-o-cha to commend the Thai government's efforts, and to offer Singapore's assistance in any way we can," said Mr Lee in a Facebook post on Thursday (July 5) evening.

He did not elaborate what assistance Singapore would be offering.

In his post, Mr Lee said he was happy to hear that the group comprising 12 boys and their coach, were found safe after being trapped in the Tham Luang cave complex in Thailand's northernmost province for close to two weeks.

"The grit and resilience of these young men is an inspiration to all. I hope that the operation to bring them out of the cave will be successful and they can be reunited with their families soon," he said.

Mr Lee noted that the operation was both difficult and grueling and commended the "strong leadership and coordination of the Thai Government and the tireless efforts of the multi-national rescue team" which led to the youths being found.

Two British divers experienced in cave rescues, John Volanthen and Rick Stanton, were first to reach the boys and were accompanied by a team of Thai navy SEALS divers.

Divers struggled through narrow passages and murky waters before finding the lucky 13 late on Monday on an elevated rock about four kilometers from the mouth of the cave. The boys were weak, but had only minor injuries.

Aged between 11 and 16, the boys went missing with their 25-year-old coach after training on June 23, when they set out to explore the caves in the forest park.

They have been given energy gels to sustain them while extraction plans were being worked out.

Rescuers now have to figure out how to get them out, through several kilometers of dangerously flooded tunnels.

One possibility is that the 13 stay put in the Tham Luang cave until the flood waters recede, at the end of the rainy season in about four months.

But some officials say the boys could be out in days if the weather is on their side and enough water can be pumped out of the cave network to enable the boys to get out the same way they got in, just before heavy downpours hit the region, on foot through muddy tunnels, perhaps with some swimming.

A third option would be to teach the boys to use scuba gear, and they then dive through the flooded tunnels, the way their rescuers reached them. A fourth possibility would be to find an alternative way into their chamber.

Mr Kobchai Boonarana, deputy director-general of the Disaster Prevention and Mitigation department, said it was up to the rescue team in the cave to decide if and when the boys would be strong enough to tackle the journey out.

"Their conditions, we can see that their morale is good but what about their strength and their ability? That's up to the team inside to decide," Mr Kobchai told reporters on Thursday.

"Our job is to keep pumping out water and it is up to the team inside to assess the safety level and whether the kids can travel safely through," he said. WITH AGENCIES