Malaysian marine police have detained seven Indonesians in waters off southern Johor, near neighbouring Singapore, believed to be responsible for a series of attacks on ships, a top official said today.

"Marine police who were on patrol in Johor waters had received information about a boat suspiciously loitering in the area late Thursday," marine police commander Abdul Rahman Ahmad told AFP.

Following a high-speed chase, marine police intercepted their boat and arrested seven Indonesians, aged between 37 to 50 years old, some 3.2 kilometres off Tanjung Stapa near Kota Tinggi, he said.

Weapons found

Abdul Rahman said police discovered five machetes, one 'rambo' knife, seven ski masks, rafia strings, binoculars, a satellite phone and mobile phone in the suspects' boat.

"With the nature of items recovered from their boat, we strongly believe they were involved in the robbery of a vessel at the Port of Tanjung Pelepas early this month," he said.

In the incident on April 8, pirates boarded a Singapore-owned oil tanker, the "Kyosei Maru" in Tanjung Pelepas port in the Singapore Strait in Malaysia's Johor state.

Pirates armed with machetes tied up the crew and robbed them of their cash and valuables.

"With their arrests, we hope to solve other pirate attacks which have taken place," Abdul Rahman added.