Police arrested 105 suspected illegal Indonesian migrants who were on a boat trying to sneak out of the country to return home, an official said today.

Marine police detained the fibreglass boat after a 30-minute chase off southern Johor before dawn Tuesday, said N Kalai Chelvan, a marine police deputy commander.

He said 89 men and 16 women, all without documents, were arrested but the boat's skipper managed to jump overboard and swim to the nearby shore to escape. He said police were acting on intelligence reports.

"This is a hot spot area," Kalai told AFP. "This is the third (seized boat) this year. But this is the biggest group."

He said marine police earlier this year had stopped two boats with about 40 people on board each time.

Around 1.2 million Indonesians are employed legally on Malaysian construction sites, in factories and other sectors, but Indonesian embassy officials estimate some 800,000 more are working illegally.

The waterway between Malaysia and neighbouring Indonesia is a popular smuggling route, also used by people from Sri Lanka, Afghanistan and other troubled countries who try to sneak into Australia via Indonesia.

Numerous boats have sunk in recent years.

- AFP