Seafarers have been warned to maintain a sharp anti-piracy watch off Indonesia's war-torn Aceh coast after eight attacks on ships within four months, the International Maritime Bureau (IMB) said today.

"We are putting out a red alert to all ships entering the Malacca Strait: Keep clear of Indonesia's Aceh coast and maintain strict anti-piracy watch," Noel Choong, the Malaysian-based IMB regional director told AFP .

"Ships are advised to sail closer to the Malaysian coast."