TORONTO - Nearly $30 million has been spent to provide security for Prime Minister Stephen Harper since he took office in 2006, newly released documents show.

And the rising cost of protecting the prime minister suggests he may have faced new threats since taking the job, a security expert says.

Harper's security costs totalled $10.7 million during his first year in office and rose to nearly $13 million in the 2007-08 fiscal year, according to documents obtained by The Canadian Press through Access to Information laws.

Partial costs for the current fiscal year totalled $5.6 million.

Those figures encompass a wide array of expenses, including transportation, communications, legal services, training, equipment -- even weapons and ammunition.

Personnel costs, including the salaries of RCMP officers who follow Harper wherever he goes, took the lion's share, rising to $9.1 million from $7.5 million in the same period.

Some information, such as the number of Mounties assigned to Harper, their pay and overtime costs were not disclosed in the documents due to security concerns. And the Prime Minister's Office did not immediately respond to requests for comment on the rising cost of security and whether they were a result of threats made against him.

But Chris Mathers, an international security expert and former RCMP officer, said the overall price tag of providing security for the prime minister is dictated by threats to his safety.

The fixed costs include having a certain number of bodyguards assigned to the prime minister, employing teams to scout locations ahead of planned visits and experts to come up with contingency plans if something goes wrong, he said.

"Whether the prime minister chokes on a chicken bone or someone tries to shoot him and he's injured, they have to know where the closest hospital is, how to get him there, is there a helicopter to Medevac him out -- right down to who takes him and who stays and shoots it out if it's a group of terrorists," Mathers said.

"Again, they're just scenarios, but all those things have to be considered."

Other costs vary from year to year, depending on the types of trips the prime minister takes and where he travels, he said.

"But primarily, the biggest variable cost when dealing with the protection of a public person is the threat assessment," Mathers said.

"And in the case of an increased threat against the prime minister, the costs will go up significantly."

The prime minister's security team has raised eyebrows for taking what appear to be extraordinary steps to ensure his safety during such routine events as policy announcements.

When Harper visited a Toronto-area electronics store last December to announce a New Year's cut to the GST, his bodyguards used trained dogs to sniff reporters' bags before they were admitted to the event.

Such measures are usually part of the protocol when Harper travels overseas to attend conferences or high-level summits with world leaders.

At the time, a spokeswoman for the prime minister dismissed the dog-sniffing sweep as "business as usual," saying security around Harper had been "tight for quite some time."

There are a number of possible reasons why security was so tight around the prime minister at the time, Mathers said.

"But the one that strikes me first is that there was probably a threat against the prime minister," he said.

"And if there's a credible threat against the prime minister, the people react quite quickly and quite strongly to it. So they have to deal with it. And those are the indicia of a threat against the PM."

Many Canadians may not realize it, but there are always threats against the prime minister, Mathers said.

"They come from nutty people mostly, but there's also perceived threats since those young guys -- those extremists out in Mississauga -- who were going to try to chop his melon off," he said.

"I think that's probably given people pause to take a look at the state of security of the prime minister and maybe we should think about making it a little bit more secure."

The plot to behead the prime minister was uncovered following the arrest of 18 people in the Toronto area in the summer of 2006 after an intense investigation involving Canada's spy agency and the RCMP.

During the trial of one of the arrested youths, the court heard police wiretaps of conversations between a police informant and the alleged ringleaders of a homegrown terrorist plot to attack Canadian targets, recorded in February 2006.

On the tapes, one of the alleged ringleaders discusses plans for a group to go to Ottawa and "cut off some heads" and "kill everybody" on Parliament Hill.

In September, an Ontario judge found the youth guilty of active membership in a homegrown Islamic terrorist cell that adhered to al-Qaida principles and was bent on bloodshed.

The cost of protecting the prime minister may carry a steep price tag, but it would probably pale in comparison to the security costs of people like U.S. president George W. Bush, Mathers said.

"Nothing is excessive," he said. "What would you do to protect your mom or dad?"