KANDAHAR, Afghanistan - The shocking deaths of five British soldiers at the hands of an Afghan National Police officer said to have been working with the Taliban appears to have done little to shake the confidence Canadian police mentors have in their local charges.

Tuesday's incident in Helmand province, in which an ANP officer opened fire on his British trainers as they relaxed following a patrol, has sent shockwaves through a NATO mission that's dependent on mentoring local police forces and exposed the potential vulnerability of Canadian soldiers who are involved in similar training efforts.

It wasn't the first time an Afghan police officer has gone rogue: two American soldiers were killed last fall in two separate incidents involving Afghan policemen who opened fire on U.S. troops.

But what happened in Helmand is unlikely to alter the relationship between Afghan police and their Canadian mentors, said Capt. Jason Quilliam, Canada's lead adviser on mentoring issues at the Provincial Reconstruction Team in Kandahar city.

"We haven't had the same problems that the British and Americans have been in," Quilliam said.

"We're always concerned with security but we haven't seen anything (alarming) with the ANP that we're working with."

Officials with the International Security Assistance Force, the official name for NATO's multinational military coalition, are investigating the incident. On Wednesday, British Prime Minister Gordon Brown told the House of Commons that the Taliban have claimed responsibility for the shooting.

The U.K.'s Guardian newspaper reported the suspected shooter, a three-year veteran of the police force who trained at a police academy in Kandahar, was now with the Taliban after having fled the scene of the shooting, a checkpoint in Helmand's Nad-e'Ali district.

The slain soldiers were identified as Warrant Officer Darren Chant, Sgt. Matthew Telford, Guardsman James Major, Acting Cpl. Steven Boote and Cpl. Nicholas Webster-Smith.

The possibility of Taliban infiltration of Afghan security forces could prove problematic for Canadians soldiers in Kandahar, where the provincial police chief admits he does not have the resources to investigate his officers.

"Among thousands of police, we can't find out who works for Taliban or who is the spy for Taliban," said Sardar Muhammad Zazai. "But I am not expecting this kind of incident in Kandahar."

Corruption and drug abuse were flagged in Ottawa's recent quarterly report on Afghanistan as significant obstacles to the further development of the ANP.

Only one of 17 ANP units based in key districts was capable of "planing, executing and sustaining near-autonomous operations," the report noted.

There are between 4,000 and 5,000 ANP officers stationed in Kandahar province.

The international community, Canada included, has a lot resting on the force's ability to secure areas that ISAF troops have cleared of insurgents.

"A big focus is on community policing, getting them out there in the community and ensuring that they're seen as a viable government authorized force," said Quilliam.

The ANP, however, typically bear the brunt of most Taliban attacks against government forces, which -- combined with already high corruption levels -- may make officers susceptible to being turned, making Afghanistan's already grim security situation even worse.

"Usually we see a downturn in the winter fighting season," said Quilliam. "The vibe we're getting is it might be a bit tougher this time around."

In a glaring example of how bad things have become, the United Nations announced Thursday it was withdrawing more than half of its international staff from the capital city of Kabul following a brazen Taliban attack on one of its guesthouses last week that left five staff members dead.

More than 600 non-essential staffers will be moved temporarily while the UN seeks to upgrade its security in Kabul.

"There is no going back to the previous situation we were in," a UN spokesperson said. "Our security clearly isn't up to the job of dealing with these kinds of attacks."