Australian authorities have been asked to play a greater role in the search for an asylum seeker boat with 150 people on board thought to be missing off the Indonesian coast.

The Australian Maritime Safety Authority (ASMA) received two distress calls early on Wednesday morning, saying the boat was sinking in Indonesia's Sunda Strait.

ASMA says it sent out an alert to shipping in the area and then passed the information to the Indonesian search and rescue organisation, Basarnas.

A spokesman for Basarnas says they sent two rescue helicopters and a boat to the area, but they returned without having found any sign of the boat or survivors.

The search was called off, but has now been expanded.

A merchant ship has been diverted to the area and Australian authorities have been asked to play a greater role in the search.

A Customs surveillance plane is due to leave Christmas Island this morning to aid in the search.

The distress calls indicated the boat was between Java and Sumatra, about 220 nautical miles from Christmas Island.

Three other boats carrying 500 people are known to have sunk on that route in recent years.

However, this boat appears to have only been about eight nautical miles from the coast.

Meanwhile, two other asylum seeker boats have been intercepted near Christmas Island.

Customs says the first had 56 passengers and two crew on board and was stopped on Tuesday night.

The second was carrying 25 people and was intercepted on Wednesday morning.

Those on board could have their asylum claims processed on Nauru or Papua New Guinea's Manus Island.