Separatist rebels destroyed a navy cargo ship Saturday just hours after a bombing blamed on the group killed 11 people in eastern Sri Lanka _ violence that casted a cloud over pivotal provincial elections scheduled for later in the day.

The government hailed the elections as a key step in restoring normalcy to the Eastern Province, which it freed from 13 years of Tamil Tiger rule last July.

Sri Lanka's military said Tamil rebels bombed and sank a navy cargo ship in the eastern port town of Trincomalee early Saturday.

Navy spokesman D.K.P. Dassanayake says the rebels attacked the ship with an underwater explosive about 2:15 a.m. He said no one was aboard and there were no injuries.

On Friday, the opposition and independent observers raised questions about the polls, accusing the ruling party of misconduct in its effort to ensure a victory it sees as its rightful reward.

Opposition candidates said former rebels allied with the government threatened them to withdraw, promised retribution against their supporters and made it nearly impossible to campaign.

"This election is a sham," said Rauff Hakeem, head of the Sri Lanka Muslim Congress, which has formed an election alliance with the opposition United National Party.

President Mahinda Rajapaksa has painted the election as a tacit referendum on his costly battle to crush the rebels in their remaining stronghold in the north and end this Indian Ocean island nation's 25-year civil war.

The rebels have been fighting since 1983 for an independent homeland for the ethnic Tamil minority in the north and east after decades of marginalization under governments controlled by the Sinhalese majority. The military, with the help of a breakaway rebel faction known as the Tamil Makkal Viduthalai Pulikal, or TMVP, seized control of the east last year.

"Nobody thought when we first liberated it ... that the government would have elections and hand over this to the people, so its very symbolic," said Basil Rajapaksa, a lawmaker and the president's brother, who is the government's point man on the region.

In a reminder the rebels could still launch deadly attacks here, the military blamed the Tamil Tigers for a parcel bomb that exploded about 5:40 p.m Friday in a small restaurant in Ampara, 130 miles east of Colombo, one of the largest towns in the province.

"This is to sabotage the election," said military spokesman Brig. Udaya Nanayakkara.

Rebel spokesman Rasiah Ilanthirayan did not answer calls for comment.

The attack was carried out despite the presence of 28,000 police officers and an extra 4,000 soldiers sent to the province to secure the polls.

The ruling party is running in a coalition with the former rebels of the TMVP, whom residents and human rights groups accuse of carrying out abductions and killings, running extortion rings and forcibly recruiting children into their ranks.

In the weeks leading up to the vote, the government announced huge grants for the impoverished region and insisted an opposition victory would bring back rebel rule.

"A vote for the government is a vote for peace and development. A vote for the opposition will be an endorsement of (Tamil Tiger leader Velupillai) Prabhakaran," President Rajapaksa told a rally last week.

However, ruling party officials were misusing government resources and the state media to bolster their chances, and tension in the province prevented many candidates from campaigning, said Kingsley Rodrigo, head of the People's Action for Free and Fair Elections, an independent election monitoring group.

"This is not a free and fair election," he said.

Arumugam Jagan, a 27-year-old Tamil construction contractor, said he decided to run after town council elections were held in March with little violence or intimidation. But the main opposition parties boycotted those polls, leaving little competition for the government and the former rebels, who won in a rout.

After Jagan announced he was running as an opposition candidate in these elections, TMVP leaders demanded he drop out and threatened retribution against him and his supporters, he said.

When he refused, his campaign posters were torn down or defaced. He canceled all public rallies under threat, and some of his volunteers quit. Others were attacked as they campaigned, they said. Like many candidates, he was forced to bring two police bodyguards with him on the campaign trail.

The head of the TMVP, known by his nom de guerre Pillaiyan, denied threatening Jagan and accused him of trying to build an asylum claim to move abroad.

Pillaiyan said it was his party _ not Jagan's _ that had been victimized. He denied allegations his group was recruiting child soldiers and threatening voters. He said his supporters remained armed _ a key point of contention in the election _ but only for self defense.

At a recent rally, a senior TMVP leader known as Jayam spoke to about 80 people sitting in a roadside clearing. When two journalists arrived, three gunmen quickly disappeared.

As the meeting broke up, a woman in a purple sari approached Jayam with a plea: His group had snatched two of her sons, including a 15-year-old. Could she have one back?

Jayam told her: "First vote, then I will sort it out."