Dozens of passengers are missing after a boat capsized as high winds whipped up rough seas off the Thai tourist island of Phuket, officials said late Thursday.

The boat was carrying 90 passengers when it capsized.

It was not immediately clear if the passengers were tourists.

Conflicting details emerged as the rescue operation carried on into the night leaving authorities scrambling to react.

The governor of southern Phuket, Noraphat Plodthong, said 49 people -- over half of the passengers -- were still "being helped" as rescue boats rushed to the scene.

He would not be drawn on whether the rescuers could see the people who had not been pulled to safety.

"There were high winds this evening," he said, adding a further 10 pleasure boats were stranded at sea.

"Yesterday we issued a warning of strong winds and storms."

But an official at the Department of Disaster Prevention and Mitigation, which is based in Bangkok, said only around 20 people were still in the sea.

"Around 70 of the passengers were rescued and taken safely to the shore," he said, requesting not to be named.

The boat was returning to Phuket from Koh Racha.

Phuket is a magnet for overseas visitors including Western sun-seekers and Chinese tourists who will make up the bulk of the 35 million people expected to visit the kingdom this year.

Footage shared on Facebook showed officials at a pier gathering information as the rescue operation unfolded in darkness behind them.

In a separate incident in the same area Thursday evening a yacht called the Senerita carrying 39 people also capsized in the high seas, the officials added.

All of the passengers were pulled from the sea alive.

Photographs circulating on social media showed soaked and apparently exhausted people in life jackets being pulled on inflatable rafts to safety.

Thailand has a sketchy health and safety record and accidents are common on its roads and busy waterways - especially during the monsoon season which is now biting.

The kingdom is already in the global spotlight for a dramatic rescue mission in the north of the country, after 12 boys and their football coach were trapped in a cave complex.