A senior figure in the Tamil Tiger rebel movement has been shot dead in eastern Sri Lanka, reports say.
The man was identified as rebel commander Ramanan
Rebel sources said the man, named Ramanan, was a commander in the district of Batticaloa.
A statement released by the Tigers said the attack was intended to end all efforts towards peace and drag the rebels into a major war.
Meanwhile the UN has condemned "despicable" attacks on humanitarian workers in the north and east.
The latest killing comes amid escalating violence in those regions. In further unrest, two soldiers died in mine attacks and a 12-year-old boy was also killed, while a foreign aid worker was injured by a grenade.
It is unclear who was responsible for the Tamil Tiger commander's killing.
One report quoted a spokesman for a breakaway rebel faction as saying it had killed the man, but a pro-rebel website accused army snipers.
It said that Ramanan's death was "a huge loss to the Batticaloa Tamil people and to the Tamil Tigers".
The statement released by the United Nations resident and humanitarian coordinator on Monday said the UN was "appalled by the continuing despicable attacks on humanitarian workers in the north and east".
Grenade attacks against three international non-governmental organisations in the eastern district of Trincomalee had resulted in serious injuries to one international staff member and two civilians, the statement added.
Last week an employee of the Norwegian Refugee Council was shot dead in the northern town of Vavuniya while returning home from work.
"We strongly condemn these attacks which undermine the ability of the humanitarian community to freely conduct operations," the statement said.
"It will instil fear into the thousands of men, women and children to whom we provide relief and assistance.
"These attacks must be investigated and the perpetrators brought to justice."
Sri Lanka has been rocked by conflict since the Tigers launched their campaign for a separate state in 1983. Some 60,000 people have died.
A truce between the government and rebels was signed four years ago, but there have been increasing ceasefire violations in recent months.