Malaysian authorities have detained more than 200 ethnic Rohingya, including five children, after they intercepted a boat off the coast of the northwestern island of Langkawi.

The wooden vessel was found adrift just over one nautical mile (2.2 kilometres) from one of the island's luxury beach resorts on Sunday morning, the Malaysian maritime enforcement agency said in a statement.

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The group of 152 men, 45 women and five children were being held at the agency's lock-ups on the mainland.

"They will be handed over to the Immigration Department for entering the country illegally," Kedah and Perlis Malaysian Maritime Enforcement Agency (MMEA) official, Captain Zulinda Ramly, said in the statement.

Malaysia, which is not a signatory to the United Nations Convention on Refugees, is a common destination for Rohingya fleeing Myanmar - where fighting continues in the western state of Rakhine - and squalid conditions at refugee camps in Bangladesh where hundreds of millions now live.

Amnesty International on Monday warned that older Rohingya refugees in the camps were being left behind in the humanitarian response to COVID-19.

The rights group said basic accurate information about the illness and measures to prevent its spread was failing to reach people in the camps, especially older refugees.

There are more than 31,500 refugees aged 60 or older among the 860,000 people in the camps, according to UN figures.

In February, at least 15 Rohingya refugees died when a vessel carrying about 130 people capsized in the Bay of Bengal while trying to reach Malaysia.

After the discovery of the boat on Sunday, the MMEA said it would also investigate complaints from the Rohingya about three alleged members of a migrant smuggling syndicate who escaped from the boat while they were still out at sea.