BATAM: Indonesia has detained a Vietnamese boat carrying two tonnes of fish that was operating illegally in its waters, officials said Wednesday, just a week after a similar high-seas pursuit.

The trawler with nine crew tossed fishing nets and other incriminating equipment overboard and then set a tyre alight in the hopes that the smoke would throw off their pursuers, Indonesian maritime authorities said.

The vessel then slammed into an Indonesian coast guard ship and a passing commercial boat in its failed bid to escape, they added.

"We fired a water cannon at the boat to stop it as it tried to get away," said coast guard spokesman Wisnu Pramandita, adding that authorities seized two tonnes of fish being stored onboard.

The incident happened on Sunday near Indonesia's Natuna islands at the edge of the South China Sea but was only made public on Wednesday.

Last week, Indonesia said it had detained two Vietnamese vessels in the same area following a dramatic high-seas brawl with dozens of crew desperate to avoid arrest.

Indonesia, the world's biggest archipelago nation, says illegal fishing costs its economy billions of dollars annually and has been trying to stop foreign vessels entering its territory.

Jakarta claims the southernmost reaches of the South China Sea as its exclusive economic zone.

In March, maritime authorities seized five Vietnamese fishing boats and nearly 70 crew in the area.