Suspected Tamil rebels infiltrated the harbor in Sri Lanka's southern port city of Galle Wednesday, and blew up three of their boats in an apparent suicide attack.

Security officials say the rebels entered the harbor in five boats posing as fishermen. At least three people were killed during the attack, including a navy sailor, and several others were wounded.

Galle is a commercial port and home to a government naval base.

Authorities imposed an indefinite curfew in Galle after the attack to help police in the hunt for rebels and to prevent reprisals against minority Tamils.

Police and witnesses say mobs tried to attack some Tamil shops after the harbor assault.

The attack in southern Sri Lanka, far from rebel strongholds in the country's north and east, could mark a shift in the Tamil guerrillas' strategy.

Galle has only recently recovered from the devastating Indian Ocean tsunami two years ago. The city's historic harbor brings in important tourist dollars for the impoverished country and is an important commercial port.

On Monday, another suicide attack by Tamil rebels killed nearly 100 sailors in northern Sri Lanka.

More than 65,000 people have been killed since rebels began their struggle for a separate homeland for the country's minority Tamils in 1983.

The guerillas and Sri Lankan government signed a truce four years ago but that pact has been in tatters for months.

Peace talks are due to take place next week on Monday and Tuesday in Geneva, Switzerland.

Some information for this report was provided by AFP, AP and Reuters.