Asylum boat shows no sign of distress

(AAP)

(AAP)

A rescue operation is under way after another asylum-seeker boat issued a distress call south of Indonesia.

An asylum-seeker boat that made a distress call en route to Australia does not appear to be in trouble, authorities say.

The boat - believed to be carrying about 85 people - called the Australian Maritime Safety Authority (AMSA) at about 10am (AEST) on Tuesday to request help.

AMSA advised the Indonesian search-and-rescue agency, BASARNAS, which is coordinating the response.

Two commercial vessels have arrived at the scene about 43 nautical miles south of West Java.

A Customs and Border Protection surveillance aircraft has also spotted the vessel, "which indicated no visible signs of distress", AMSA said.

HMAS Childers and ACV Triton have also been deployed.

The boat appears to be the latest to call for help shortly after leaving Indonesia, even though it is not actually in distress.

A boat carrying up to 180 people appeared to use a similar tactic last week.

Nevertheless, rescuers are on high alert after two boat disasters last month.

A boat carrying about 200 people capsized on June 21 on its way to Christmas Island, leaving an estimated 90 people dead.

Another boat carrying 134 people sank on June 27, leaving four people dead.

Meanwhile, a suspected asylum-seeker vessel carrying seven people was intercepted northwest of Christmas Island on Tuesday afternoon.

The passengers are now being taken to the island for security, health and identity checks.