The U.N. said Thursday that it will keep its aid workers in Sri Lanka despite the accusation by European truce monitors that Sri Lankan security forces were behind the killings of 17 private relief agency employees this month.

The finding prompted U.N. humanitarian chief Jan Egeland to say Wednesday that, "We cannot continue in this area unless we know that people will be held accountable for the execution of 17 of our colleagues."

CountryWatch: Sri Lanka

A spokeswoman for Egeland's office in Geneva described that as "a warning" and said the U.N. had no immediate plans to pull out.

"U.N. humanitarian workers continue their efforts and will continue to do their jobs, taking into account the current security conditions in Sri Lanka," Office for the Coordination of Humanitarian Affairs spokeswoman Elisabeth Byrs said. "At the moment, there is of course no withdrawal. But if a tragedy were to occur like what happened, we would have to think things over."

The Nordic team in charge of monitoring the country's now-disintegrating 2002 cease-fire accord said in a statement Wednesday that it was "convinced" that Sri Lanka's security forces were behind the slayings and that the government had blocked their investigation to cover up the incident. The government vehemently denied the allegations.

Bodies of the workers for the international relief agency Action Against Hunger were found Aug. 7 shot execution-style amid a fierce battle between the government and the separatist Tamil Tiger rebels for the eastern town of Muttur.

The aid workers — all but one members of the ethnic minority Tamil ethnic group — were working on tsunami-relief projects in Muttur.

The slayings prompted an international outcry, with U.N Secretary-General Kofi Annan calling for a thorough investigation.

Speculation had focused on the Sinhalese-dominated security forces because the workers were staying in a part of town firmly in control of the government. Sinhalese and Tamils have a long history of ethnic rivalry.

"Taking into consideration the fact that the security forces had been present in Muttur at the time of the incident, it appears highly unlikely to blame other groups for the killing," the monitors' statement said.

Based on its investigation and interviews, the group said it is "convinced that there cannot be any other armed groups than the Security Forces who could actually have been behind the act."

Spokesman Thorfinnur Omarsson said that the team had interviewed hospital staff, police, families of the dead workers and eyewitnesses.

The government prevented investigators them from reaching the area to investigate the killings, and had no reason to do so except to "conceal the matter," the monitoring mission said.

The government reacted furiously, describing the statement as "pathetic" and biased.

"We deny it, and it's a totally baseless statement," government spokesman Keheliya Rambukwella said. "It's pathetic and it's biased and they have no right make such a statement because they are not professionals in autopsy or post-mortem."

He said according to police reports, the Tamil Tigers were in control of Muttur from Aug. 2-5 and that the post-mortem reports on the aid workers suggested they were killed between the night of Aug. 3 and the following day.

The outgoing head of the monitoring team, Ulf Henricsson, called the killings "one of the most serious recent crimes against humanitarian aid workers worldwide."

In Paris, Action Against Hunger said it had taken note of the truce monitors' statement and said it waiting for more information before commenting further.

"Action Against Hunger wants all light to be shed on the circumstances and responsibilities of the massacre in Muttur," it said in a statement.

Henricsson urged the government to take all necessary steps to stop any kind of violence against civilians and thoroughly investigate the killings.

Jeevan Thiagarajah, executive director of the Consortium of Humanitarian Agencies, said he hoped the finding would bring more international scrutiny to the civil war engulfing Sri Lanka for more than two decades, especially on the issues of "human principles and accountability."

The Consortium for Humanitarian Agencies is an umbrella of local and international non-governmental organizations working in Sri Lanka.

Sri Lanka's Tamil Tigers have been fighting since 1983 for a separate homeland for the country's 3.2 million Tamils in the north and east.

The 2002 cease-fire temporarily halted large-scale hostilities in which as many as 65,000 people died, but the last few months have seen the two sides engage in open warfare along their shared borders.