Sri Lankan President Mahinda Rajapakse vowed to protect his nation's sovereignty, threatening Tamil Tiger rebels with tough action if they don't end spiraling violence that claimed at least 13 more lives over the weekend.

The violence adds to fears that a 2002 cease-fire between the rebels and government could collapse, plunging the island nation back into civil war.

Rajapakse said he would not hesitate to take stern action if the Liberation Tigers of Tamil Eelam rebels continue to unleash attacks on security forces.

"If they insist on continuing their attacks, I will have to defend my country," Rajapakse said in an interview published in Colombo's Sunday Times.

"I have vowed to protect the sovereignty and territorial integrity of Sri Lanka," Rajapakse was quoted as saying.

The violence has killed more than 180 people since the start of April, jeopardizing efforts by Norwegian peace brokers to restart peace talks.

On Sunday, unidentified gunman fatally shot two suspected rebels in northeastern Trincomalee, police said, hours after a Tamil resident was killed in northern Jaffna.

Also Sunday, troops shot and killed a rebel who attacked an army checkpoint in Jaffna with hand grenades, said military spokesman Brig. Prasad Samarasinghe, adding that three other suspected rebels were arrested.

One soldier was wounded in the attack, he said.

Separately, suspected rebels killed a member of a breakaway faction late Saturday in eastern Batticaloa.

Also on Saturday, eight people including a 4-month-old baby, a 4-year-old boy and their parents were killed by gunmen in disputed circumstances.

TamilNet, a pro-rebel Web site, claimed that navy forces surrounded a home in the village of Allaipiddy on the northern Jaffna peninsula and opened fire on the house.

The government denied any military involvement and blamed the killings on the Tigers, saying in a statement they were attempting to "divert international opinion."

Local residents, speaking on condition of anonymity because of fears of retribution, said unidentified men had raided a home and killed the eight residents in a hail of gunfire.

The motive was not known.

CountryWatch: Sri Lanka

Rajapakse's comments came after the rebels threatened to resume war if they are denied access to the sea adjoining areas they control.

The threat of renewed warfare by the rebels is the latest in a steady escalation of tensions.

"We will not hesitate to wage war with anyone who attempts to prevent us from exercising our freedom," Col. Soosai, who heads the Sea Tigers, the rebels' naval wing, was quoted as saying by TamilNet on Saturday.

The warning came just days after rebel suicide boats rammed and sank a navy patrol craft. The attack Thursday and a subsequent sea battle killed dozens of people.

Separately, European truce monitors announced they were suspending sea monitoring missions after rebels said they could be in danger from Tamil Tiger attacks.

The Tigers began fighting in 1983 to create a separate state for ethnic minority Tamils, accusing the majority Sinhalese of discrimination. More than 65,000 people died in the conflict before the 2002 truce.