By Ranga Sirilal

COLOMBO, May 10 (Reuters) - A rebel Black Tiger suicide squad sank a Sri Lanka naval vessel in the eastern port of Trincomalee on Saturday, the second attack in the area in hours as locals readied to go to the polls.

The military reported no naval casualties in the attack which took place after a bomb killed 11 people in a crowded cafe also in the east on Friday night.

The elections are part of the government's blueprint for devolution in minority Tamil areas. It hopes the vote, the first of its kind in the region in two decades, will go hand-in-hand with a push to win the war in which tens of thousands of people have died.

Navy spokesman Commander D.K.P Dassanayake said a logistics vessel had been hit by an underwater explosion in Saturday's attack.

The Tigers, fighting for an independent state in the north and east, were not available for comment on the attack but pro-rebel website www.tamilnet.com quoted rebels as saying that a supply ship had been sunk.

Tamilnet said Black Tigers, or underwater suicide bombers, had attacked the vessel at 2:23 a.m. "The attack was carried out when the supply vessel was loaded with explosives to be transported to KKS Harbour in Jaffna," it said.

Analysts say both the government and rebels often inflate enemy death tolls and play down their own losses. The reports are rarely possible to verify independently.

After driving the Tamil Tiger rebels from the east, the armed forces are now focused on Tiger-held areas in north, intensifying fighting in a 25-year-old civil war that has killed an estimated 70,000 people since 1983.

Fighting between government forces and the Liberation Tigers of Tamil Eelam (LTTE) has intensified since the government formally pulled out of a 6-year-old ceasefire pact in January, though a renewed civil war has been raging since 2006.

Security had been tightened for Saturday's polls in the districts of Trincomalee, Ampara and Batticaloa. (Editing by Jeremy Laurence)

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