The Taliban has sent an open letter urging Canadians to push Ottawa to leave Afghanistan or face more insurgent attacks, after two Canadian aid workers were killed.

The fundamentalist Islamic group has waged a violent campaign against NATO and Afghan forces since 2001 when the Taliban was ousted in a U.S.-led invasion of Afghanistan.

In an open letter written on behalf of the "Islamic Emirate of Afghanistan" and addressed to the "Canadian people," the Taliban says Canada should not have followed the "American" agenda and has "sacrificed" its self-respect.

The letter, purportedly written by Taliban spokesperson Qari Muhammad Yussef, says the Taliban is forced to kill Canadians because innocent Afghans are being killed.

"The Afghans did not go to Canada to kill the Canadians. Rather, it is the Canadians who came to Afghanistan to kill and torture the Afghan, to please the fascist regime of America," the letter said.

"The Canadian people have to realize if their sisters, their brothers and their children are being killed in Afghanistan, it is because of the wrong policy of the government of Canada and their falling under the influence of others when they sent occupation soldiers to Afghanistan."

The letter told Canadians to prepare for more attacks like the one earlier this past week in which two Canadian aid workers were gunned down in Logar province.

"Events such as Logar will happen again, because occupied Afghanistan looks at all actors that are established in the interest of America with an eye of hostility," said the letter, which was dated Aug. 15.

"You have to convince your government to put an end to the occupation of Afghanistan so that the Afghans are not killed with your hands and so that you are not killed with the hands of the Afghans."

A spokesperson for Prime Minister Stephen Harper called the letter a propaganda exercise and said the threats in it will have no effect on Canadian policy. Kory Teneycke also said it's not surprising the Taliban are targeting aid workers considering that they attack their own civilians.

The letter was released on a weekend that saw deadly violence throughout Afghanistan, with more than 90 people reported killed over four days. There were reports that:

• Afghan authorities killed 32 Taliban fighters during a four hour battle on Sunday. Five private security guards also died.
• Ten Afghan police officers were killed by a roadside bomb while on patrol in Kandahar province on Saturday.
• Foreign forces and Afghan troops killed seven militants in clashes Saturday in a mountainous area of Zabul province. Similar clashes between police and militants also left four insurgents dead in eastern Paktika province. Three police officers were wounded.
• Four police officers were killed on Friday during an insurgent attack that left 23 militants dead in southern Helmand province.

According to the Afghanistan NGO Safety Office, which tracks security issues in the country, insurgent attacks were up by 50 per cent in the first half of this year. About 3,200 people, mostly militants, have died in insurgent attacks this year.

The insurgent violence has left Afghan authorities concerned about security at upcoming celebrations for the country's Independence Day celebrations on Monday. They've called in more than 7,000 officers to secure Kabul. Kandahar's provincial police chief says he will also beef up security in the province, which is the base for most of Canada's 2,500 soldiers in Afghanistan.

With files from The Canadian Press