Indonesian authorities were searching Thursday for a boat believed to be carrying asylum seekers to Australia that went missing off eastern Indonesia, officials said.

The search was launched after reports of a capsized boat, the police spokesman of West Nusa Tenggara province, Sutarman Husain, told AFP.

"We received information in the afternoon from fishermen that a boat with dozens of people had capsized off Sumbawa island," in eastern Indonesia, he said.

Murtadi, a search and rescue official in the province who goes by one name, said his force had also received information that the boat was loaded with about 50 asylum seekers and was en route to Australia's Christmas island.

Search and rescue officials said they would intensify the search on Friday morning, using helicopters.

On Sunday a Singapore-registered tanker rescued around 120 Australia-bound asylum seekers -- all males and mostly Afghans and some Iranians -- from their sinking wooden boat.

They finally disembarked in Indonesia, after refusing to get off the docked tanker for two days, insisting they be allowed to continue their journey to Australia.

Thousands of asylum seekers head through Southeast Asian countries on their way to Australia every year and many link up with people smugglers in Indonesia for the dangerous voyage, often on rickety, overloaded boats.

In December, a boat carrying around 250 mostly Afghan and Iranian asylum seekers sank in Indonesian waters on its way to Christmas Island, with only 47 surviving.

Indonesia is not a signatory to the UN refugee convention and often jails asylum seekers awaiting refugee status.