The warning was the strongest since the two sides signed a cease-fire five years ago and came during a meeting between Norwegian ambassador Hans Brattskar and SP Thamilselvan, the Tamil rebel political chief, the rebels said in an e-mailed statement.

Accusing the military of amassing weapons and fighters, Thamilselvan told Brattskar that the Tamil Tigers also were ready for combat.

"Thamilselvan said he emphasized to the ambassador that the present soft approach of the international community toward the GoSL (Sri Lankan government) is not going change its plans and will only contribute to a worsening situation leading to bloodbath in the island," the rebels' statement said.

The statement went on to accuse the government of making movements of personnel and equipment closer to the rebels' territory and stated that the rebels were expecting a large-scale attack against them soon.

No comment was immediately available from the Sri Lankan government, whose military in the past five months has driven rebels from many of their bases, mainly in eastern Sri Lanka.

Hours before the rebel warning, the insurgents killed three Sri Lankan soldiers in the island's north early Monday.

The rebels attacked a military camp in the northern Jaffna peninsula just after midnight, and the ensuing battle lasted for an hour, said Lt. Col Upali Rajapakse, a senior official at the information unit of the Ministry of Defence.

Seven people have been killed in Sri Lanka's restive northern and eastern regions in clashes between security forces and Tamil Tiger rebels, the defence ministry said Monday.

Three soldiers were killed in the northern district of Jaffna early Monday when troops traded fire with Tiger rebels, the military said, adding that security forces had also inflicted heavy damage on the guerrillas. It gave no further details.

In the eastern district of Ampara, a police commando was killed on Sunday when forces encountered a rebel group during a foot patrol.

Meanwhile, police said late Sunday they had found the bodies of two civilians shot dead by unidentified gunmen in the eastern district of Batticaloa.

Elsewhere in the north, police found the body of a Tamil youth who had been shot dead tied to a lamp post.

There was no immediate word from the Tamil Tigers.

Escalating violence in the past year has all but destroyed a Norway-brokered 2002 cease-fire agreement. European peace monitors say the fighting has killed at least 4,000 civilians and combatants since December 2005.