The Indonesian navy prevented a suspected migrant boat from entering the country's waters at the weekend after the arrival of hundreds of Rohingya and Bangladeshis and has stepped up patrols in the area, the military said Monday.
Nearly 3,000 migrants have swum to shore or been rescued off Indonesia, Malaysia and Thailand over the past week, around half of whom have arrived in Indonesia's western province of Aceh.
The three nations have sparked outrage by turning away some overloaded vessels, and thousands of migrants are still believed to be stranded at sea after a Thai crackdown disrupted long-established people-smuggling and -trafficking routes.
The migrants who have made it to shore in Indonesia have mostly been rescued by fishermen, and grim tales have emerged of deadly fights on board and harsh treatment by people-smugglers.
On Sunday the Indonesian navy stopped a boat from entering its waters after the vessel was spotted heading across the Malacca Strait from the direction of Malaysia, Indonesian armed forces spokesman Fuad Basya told AFP.
After radio communication with the boat, it turned back from Indonesia, he said, adding it was not physically pushed back. Basya said it was believed the boat was carrying more migrants, although he was not sure how many. "It was heading to Indonesian waters from Malaysia and was denied entry," Basya said.
"It was intercepted, and we stopped it from passing." A week ago the navy stopped a boat carrying hundreds of migrants from entering Indonesia, and the military insists it will only help vessels in distress.
Basya said four warships and one plane were now patrolling off Aceh's coast to stop migrant boats from entering, up from one warship and a plane around a week ago. "The boats are forbidden from entering Indonesia," he said.
On Friday fishermen rescued hundreds of migrants from a sinking boat off Aceh, on the huge island of Sumatra. Fighting had erupted on board between the Rohingya, a persecuted Muslim minority from Myanmar and the Bangladeshis, and many leapt or were thrown overboard.
Southeast Asian nations are under growing pressure to take action to stem the influx of boatpeople, and Malaysia, current chair of regional grouping ASEAN, on Sunday pressed Myanmar to engage in talks on the issue.
Malaysian Foreign Minister Anifah Aman is also due to host talks with his Indonesian and Thai counterparts this week.
However, Malaysia also said last week it would turn away boats bearing desperate migrants from Myanmar and Bangladesh unless they are in imminent danger of sinking, following in the footsteps of Indonesia.
Meanwhile families of Rohingya on board one of the boats were growing worried as they had not been able to contact their loved ones since Saturday, Chris Lewa of the Arakan Project, which monitors migrant journeys across the Bay of Bengal, told AFP.
The boat is believed to be carrying around 350 people including dozens of women and children and was thought to be cast adrift by a Thai smuggling gang who fled the vessel after disabling the ship's engine earlier this month. Lewa said they and relatives had been able to reach migrants on board the boat via mobile phones but the numbers have been dead since Saturday evening.
It is not clear whether that boat is the same vessel spotted by journalists last Thursday.