The boat, crewed by five members, was detected near Trincomalee on the island nation's east coast with 50 men, 11 women and three children aboard as passengers, navy spokesman Indika de Silva told AFP.

"The boat had just left from somewhere along the Trincomalee coast when it was detected by a navy craft," he said.

"The suspects will be handed over to the police for further investigations."

Four other boats aiming to ferry passengers to Australia had attempted to embark from Sri Lanka in the past month, he said, adding that 300 people had been arrested for immigration-related offences over the same timeframe.

Security officials have said Sri Lanka's worsening economic crisis may be encouraging illegal emigration.

The country has for months faced severe shortages of food, fuel and medicines after running out of foreign exchange to import essential goods.

Australia's hardline immigration stance bans anyone who arrives by boat without authorisation from staying permanently.

Christmas Island, the nearest Australian territory to Sri Lanka, is located about 3,500km southeast of Sri Lanka. The Australian mainland is 5,500km from the South Asian country.