The operation to free 12 boys and their coach trapped in a cave in northern Thailand is running “smoothly”, the head of the operation says.

Four boys have been brought above ground so far in good health, rescuers say.

The mission has now been paused for at least 10 hours as air tanks need to be replaced.

Rescuers decided to go ahead with the hazardous operation on Sunday because of fears of rising waters.

The next phase would begin on Monday morning, after relaying “all of the air tanks and all systems along the way”, Chiang Rai Governor Narongsak Osottanakorn said.

He corrected earlier reports that said six boys had been freed.