Two separate ambushes in northeastern Sri Lanka have killed at least three security forces and wounded three more in the latest violence threatening the nation's fragile cease-fire.

Friday's mine attacks in the port city of Trincomalee also sparked intercommunal clashes near the city. The violence killed one person and damaged several houses. The latest killings bring the death toll to 63 in two weeks.

The clashes came a day after Tamil rebel leaders pulled out of next week's peace talks with the government. They say they will not attend the talks until violence ends in Tamil majority areas in the north and east of the country.

The rebels accuse the military and armed anti-rebel groups of killing Tamil civilians. The government denies the charge.

A Norwegian peace envoy, Jon Hanssen-Bauer, has been meeting with rebel leaders and government officials in an effort to salvage the more than four-year-old cease-fire.

Tamil rebels have been fighting since 1983 for a separate homeland in the Tamil-dominated north and east. More than 60,000 people were killed in the fighting before the 2002 cease-fire.

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