A rescue operation to save 12 boys and their football coach trapped in a cave in northern Thailand for more than two weeks is in progress.

It comes a day after the head of the rescue mission said conditions were "perfect" for the evacuation to begin, and amid fears that incoming monsoon rains could soon thwart the plan.

Helicopters are on standby to fly the group to hospital for treatment, following their underground ordeal.

Image: The 12 boys and their football coach have been trapped in the cave network for over two weeks

Rescue chief Narongsak Osottanakorn told journalists near the Tham Luang cave site: "Today is the D-day. The boys are ready to face any challenges."

He said 13 foreign divers, five Thai divers and five Navy SEALs were involved in the rescue bid and the plan was for the boys to gradually come out, accompanied by two divers each.


Image: Rescuers face a series of challenges to bring the boys to safety

Officials say the quickest time that the boys could be brought out of the cave is 9pm local time (3pm UK time) on Sunday, and the mission could take up to four days.

The only way to extract them is by navigating 2.5 miles of dark and tight passageways filled with muddy water and strong currents, as well as oxygen-depleted air.

Rescue commander: 'We're at the peak of readiness'

Experienced cave rescue experts consider an underwater escape a last resort, especially as the boys are untrained in diving.

The path out is considered especially complicated because of twists and turns in narrow, flooded passageways.

On Saturday, Mr Narongsak said mild weather and falling water levels over the past few days had created "optimal conditions" for an evacuation that would not last if it rains heavily again.

An hour before the rescue mission began, officials ordered the media and "non-essential personnel" out of the immediate area.

Making the announcement over a loudspeaker, a police spokesman said: "Everyone who is not involved with the operations has to get out of the area immediately.

"From the situation assessment, we need to use the area to help victims."

The boys, aged between 11 and 16, and their 25-year-old coach became stranded when they went exploring in the cave after a practice football game.

Trapped Thai boys write heartfelt letters to their parents

Flooding cut off their escape but they were found by British cave diving specialists nine days later, dishevelled and hungry, on a ledge several miles inside the cave.

But with some of them unable to swim and having no diving experience, Mr Narongsak had previously dubbed the rescue effort "Mission Impossible".

Cave rescue may take up to four days

The death of a former Thai Navy SEAL diver who ran out of oxygen in the cave last week underscored the danger of the route even for experts.

After a short deluge of rain on Saturday night and with more downpours forecast later on Sunday, Mr Narongsak said authorities had to act immediately.

"There is no other day that we are more ready than today," he said. "Otherwise we will lose the opportunity."