Rebels mounted a fierce offensive Saturday in Sri Lanka's northern Jaffna Peninsula, the heart of the island's Tamil minority, military officials and the rebels said amid the heaviest fighting since the two sides signed a 2002 cease-fire.

Thousands of civilians were reported trapped by the fighting, much of it focused around the village of Muhamalai, a dividing line between territories controlled by the government and the Tamil rebels — and a strategic spot along the only highway into the core of the peninsula.

More than 200 rebels and 27 government soldiers died in Saturday's fighting, which continued as night fell, said a military spokesman, Brig. Athula Jayawardana. Eighty government soldiers were wounded, he said.

Rebel officials could not be reached for comment on their casualties, and the government's report could not be confirmed.

CountryWatch: Sri Lanka

The combat zone has been sealed off to outsiders, and there was no way to independently confirm the situation. The government controls most of the peninsula, which is the traditional home of Sri Lanka's 3.2 million ethnic Tamils, who accuse the 14 million Sinhalese who dominate the island of discrimination.

Saturday's fighting began with the rebels launching attacks on navy camps in the town of Trincomalee and then striking at government forces in Muhamalai and elsewhere, Jayawardana said.

A pro-rebel Web site, TamilNet, said the insurgents captured an army checkpoint at Muhamalai, but a statement from the defense ministry said that soldiers had beaten them back.

An ethnic Tamil lawmaker said civilians in parts of the peninsula were trapped by heavy fighting because of a government curfew and did not have electricity or telephone service.

"People are not allowed to move to save their lives. The Sri Lankan government, by imposing a curfew, has kept them as human shields," said Nadaraja Raviraj, a lawmaker from Jaffna.

There was no immediate comment from the government.

Meanwhile, a senior Sri Lankan official was shot to death at his home in suburb of Colombo, the capital. It was not immediately clear who was responsible, police said.

Ketheesh Loganathan was deputy head of the Peace Secretariat, which coordinates the government's dealings under the Norway-brokered peace process with the rebels. He was formerly a political adviser to another Tamil separatist group that disarmed in 1987 and has opposed the Tamil Tigers.

The 2002 cease-fire was intended to halt more than two decades of bloodshed between the government and the Liberation Tigers of Tamil Eelam, which has been fighting since 1983 for an independent homeland for ethnic Tamils in the north and east of the country.

While the cease-fire remains officially in effect, it has been left in shreds by weeks of fighting.

The latest conflict started when the rebels blocked the flow of water from a reservoir to government-held villages in the northeast July 20, accusing officials of backtracking on a pledge to boost water to rebel-held areas. After days of fighting the sluice was reopened, with both sides claiming credit for ending the water crisis.