Suspected Tamil Tiger rebels ambushed and killed 13 Sri Lankan sailors in an attack on a naval convoy in northern Sri Lanka today in the worst breach of a 2002 ceasefire so far, the military said.
"They laid a deliberate ambush - it was very well carried out," said an army spokesman. "They fixed four claymores. All of them were blasted.
"They fired five RPG rounds and then small-arms. When we got to the scene we found 12 dead bodies and three wounded, but one of them died."
The Tamil Tiger rebels were unavailable for comment, but the army said no one else had the capacity to mount such an attack.
It took place near the Mannar Sea between Sri Lanka and India, the scene of a naval clash on Thursday that the Tigers say killed three sailors in the first attack at sea since the truce.
Clashes between the military and rebels have been rising since the Tigers threatened a return to war during 2006 if they did not get concessions from the government. Two claymore mine attacks earlier in the month killed 14 soldiers.
At least 64,000 people have been killed in Sri Lanka's two-decade old civil war.
Nordic truce monitors said they did not yet have details of the latest incident but that it was an extremely worrying development at a time when the two sides are unable to agree on a venue for peace talks, let alone discuss rebel demands for a Tamil homeland.
"The military have sealed off the area," Sri Lanka Monitoring Mission chief Hagrup Haukland said.
"It is very, very serious - it's really adding petrol to an ongoing situation."