The arrival of the boat presents an added complication for the Abbott government, whose attention has been trained north as it attempts to stem the Indonesian flow.
At about 11.30am local time residents on the tiny islands noticed what appeared to be a Sri Lankan fishing boat off the west coast of the Cocos and Keeling Islands.
Amid fierce swells a Customs boat motored out to intercept the boat.
Cocos resident Karen Willshaw said the boat would have had to contend with “massive big swells” that have recently been battering the island.
“Customs had no knowledge of it, apparently,” Ms Willshaw told The Australian.
“We’ve had P3 flying here — they hadn’t spotted it.”
When the Sri Lankan smuggling trade was booming, Cocos Island became the destination of choice for asylum-seekers, who could shave days off the dangerous voyage by targeting the island, which sits 2750km west-northwest of Perth in the Indian Ocean.
Last night Sri Lankan high commissioner Thisara Samarasinghe said his country had made a massive effort to stop people-smugglers sending boats to Australia.
“Maybe a few boats do slip through,” he said. “The people-smugglers throw their money in every direction.”
Admiral Samarasinghe said that because of co-operation between his country and Australia, only a very small proportion of asylum-seekers were from Sri Lanka.
About 2000 Sri Lankans had been sent home, Admiral Samarasinghe said.
When in opposition, the Coalition foreshadowed intercepting Sri Lankan asylum boats on the high seas and returning them to Sri Lanka, a proposal enthusiastically endorsed by Colombo, which denies that any its citizens require refugee protection.
Ms Willshaw said it had been “four or five months, easily” since a boat last arrived at Cocos.
“We really thought they’d given up,” Ms Willshaw said.
“All the (Immigration Department) people have left Cocos and they’re down to minimal Customs people as well. Looks like they might have to start sending people back here.