A boat carrying 153 Tamil asylum seekers is heading towards Christmas Island, refugee activists say.
The 21-metre boat, which left from India, is said to have sprung an oil leak and is 300km west of Christmas Island.
"The boat is making very slow headway, but they do have an oil leak and are concerned that they will run out of oil before they reach Christmas Island," Refugee Action Coalition spokesman Ian Rintoul said on Friday.
Mr Rintoul said he had spoken to an asylum seeker on board, and said Australia was the only country in the region with the rescue capabilities to ensure their safety.
"We are extremely concerned that the government may attempt to divert the asylum seekers or leave assistance until it is too late," Mr Rintoul said.
A spokesman for Immigration and Border Protection Minister Scott Morrison said the government's border protection policies had not changed.
"For operational security reasons, the government does not confirm or otherwise comment on reports of on-water activities in relation to Operation Sovereign Borders or disclose details of any operations other than where there have been significant events involving extreme risk of safety of life at sea," he said.
"The government has no such reports of significant events."
Mr Rintoul said people on the boat had made contact with Australian maritime rescue authorities.
"They are asking for help," Mr Rintoul said.
He said the boat had 153 asylum seekers, including 32 women and 37 children.
Mr Rintoul said the boat was a similar distance from Christmas Island as it was from Indonesia.
