Severe flooding across the south of Thailand has killed at least 15 people and stranded thousands of tourists.

Victims were either swept away by the rising waters or buried in mudslides caused by the unseasonable downpours.

Trains to the region have been cancelled and several airports shut. Flights are now landing at Koh Samui, but a backlog is causing long delays.

The Thai navy has evacuated about 1,200 stranded tourists from Koh Samui and Koh Tao on its only aircraft carrier.

"There are roughly one million people affected in many provinces. At first we thought the flood would last a day or two, but now it has already been one week," deputy prime minister Suthep Thaugsuban said.

The provinces of Chumphon, Nakhon Si Thammarat, Surat Thani, Trang, Krabi and Phatthalung have been the hardest hit. Rising floodwaters have hampered relief efforts.

Tourists stuck

Air travel, road and rail links have been flooded and electricity cut to many areas. A total of 80 districts in eight provinces have been declared disaster areas.

A British embassy spokesman told the BBC a team on its way to Koh Samui would initially be based at the airport to assist British nationals.

Some 13,000 holidaymakers are said to have been stranded on Koh Samui alone, according to the island's tourism association.

The agency warned that food and fuel stocks could run low in the next few days.

"We advised tourists to stay in hotels and not to travel to the airport until the situation returns to normal. So far food and utilities are still adequate, but I worry about stocks of diesel," Bannasat Ruangjan was quoted by AFP as saying.

Another 800 tourists stuck in Bangkok had been hoping to go to the island for a holiday, before 50 flights were grounded this week.

Police told the BBC that landslides in Krabi have killed two people and left at least 20 people missing.

One tourist, Lucy Pennington from London, said on Twitter that Railay Beach, in Krabi province, was inundated with water.

"Holiday turning into nightmare. Escaped Railay today, everywhere flooding and I don't know how to get to Bangkok," she said.

Floods late last year in the south of Thailand left more than 200 people dead.

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