The United Nations has threatened to suspend its aid operations in Sri Lanka after truce monitors accused government forces of executing aid workers in the civil war-torn country.

International ceasefire monitors blamed government troops Wednesday for the killing of 17 aid workers earlier this month.

The men and women, who worked on tsunami relief projects for Action Against Hunger, were found face down in their office compound and had been shot in the head at close range.

All but one of the victims were members of the minority Tamil community.

The Sri Lankan government denies any involvement in the deaths and accused the Nordic truce monitors of being biased in favour of the rebel Tamil Tigers.

The International Red Cross said the fighting in northern Sri Lanka is so intense that it's no longer safe to take foreigners out by ship.

Hundreds of people have been killed this month alone after a ceasefire between the government and the Tamil Tigers fell apart.

Calls for Canadian involvement

The situation has prompted renewed calls for the Canadian government to get more involved in trying to solve the ethnic dispute.

With so much violence in Iraq and Afghanistan, the return to a brutal civil war in Sri Lanka has garnered little attention here in Canada, which has frustrated Canada's Tamil community, said David Poopalapillai, spokesman for the Canadian Tamil Congress.

"We are being ignored," Poopalapillai said. "Canada has engaged itself and been able to resolve many conflicts in the world, why not in Sri Lanka? Why are we not being heard?

Liberal leadership hopeful Bob Rae, who has worked with an international agency to try to bring peace to the embattled country, said it is time for Canada to get more involved.

"The situation is really deteriorating — assassinations, landmines, planes strafing orphanages where dozens of young people were killed," Rae told CBC News.  

Rae said he believes countries giving aid to Sri Lanka, such as Canada, should put more pressure on both the government and the rebels to negotiate an end to the conflict, but are too distracted by other matters.

"The trouble with the world today is you just can't say, 'we've got a crisis here today. Sorry, we'll get to you in a minute,'" he said.

Rae said he was devastated by the death of his friend, Kethesh Loganathan, a Tamil activist working with the government who was assassinated a couple of weeks ago.

Another of Rae's friends, Sri Lankan foreign minister Lakshman Kadirgamar, was assassinated a year ago while stepping out of his pool.

"It's haunted me," Rae said.

On Wednesday, Prime Minister Stephen Harper insisted the Conservatives aren't ignoring the conflict.

"Our government has been actively engaged with the international community — with the Norwegian interlocutor and others in trying to urge negotiations," Harper said.

But Harper added both sides don't seem much interested in talking at the moment.

After coming to power, the Conservatives put the Tamil Tigers on a list of banned terrorist groups — something the former Liberal government refused to do.