At least seven people have died after a boat carrying undocumented migrants sank near the border between Thailand and Malaysia.

Thirteen people have been rescued but hundreds are missing - they were among a group of 300 people, most of whom are Rohingyas, who left Myanmar's impoverished Rakhine state two weeks ago on a larger vessel before splitting onto small boats, said a Malaysian maritime official.

The capsized vessel is believed to have gone down near the resort island of Langkawi, the Malaysian Coast Guard said.

Rescue efforts have entered a second day, with the search area expanded from 170 to 256 square nautical miles. Malaysia's maritime authority expects the search to last seven days.

The body found in the water on Sunday was that of a Rohingya woman, Malaysia's state-owned news agency Bernama reported.

Of the 13 rescued, 11 are Rohingyas and two are Bangladeshis.

The sunken boat was carrying about 70 people, while the status of the boats carrying the remaining migrants are "unclear", Malaysian authorities said on Monday.

The Rohingyas, who are primarily Muslim, are one of the many ethnic minorities in the predominantly Buddhist country, but they are denied citizenship by the government of Myanmar.

Since August 2017, a deadly crackdown by Myanmar's army sent hundreds of thousands of Rohingyas fleeing across the border into Bangladesh.

Conflict and poor living conditions in Bangladesh however have also prompted some Rohingyas to make precarious journeys on overcrowded vessels to Malaysia, a Muslim country which some envision to be a safe haven in the region.

Officials say many of them would have each paid more than $3,000 (£2,300) for these passages by sea.

These boats are often small and cramped, lacking in basic facilities like water and sanitation.

And they do not always make it to Malaysia. Some die while being stranded at sea, while others are sometimes detained or deported. (BBC)