More Lankans forced to return home

Another 30 Sri Lankan asylum seekers who arrived in Australia by boat have been sent home.Immigration Minister Chris Bowen says the men were "involuntarily" returned to Colombo on a charter flight on Thursday.

It brings to 186 the number of Sri Lankan asylum seekers the government has sent home since it embraced its tough new immigration policies in mid-August.

Mr Bowen said the men raised no issues that engaged Australia's international obligations.

"Without a valid visa they had no legal right to remain in Australia and were removed at the earliest opportunity," Mr Bowen said in a statement on Thursday.

The government would continue to regularly transfer asylum seekers to Nauru and would shortly start sending people to Manus Island too, the minister said.

"And where appropriate, the government will certainly continue to return people where they do not engage Australia's international obligations," he said.

Mr Bowen's announcement came as a boat carrying 35 people was intercepted near the Cocos Islands.

Coalition immigration spokesman Scott Morrison says it is the 500th boat to arrive since Labor was elected in 2007.

"Today is a dark day for Australia," Mr Morrison said in a statement.

"This milestone has come with great cost, chaos and tragedy. The only winners are the people smugglers."

More than 750 asylum seekers have arrived on 15 boats in just the past eight days. (AAP)