The al Qaeda-inspired group The Islamic State of Iraq and the Levant (ISIS) is setting its sights on the Iraqi capital, after capturing the northern town of Tal Afar early Monday. But the advancement of ISIS couldn't have been possible without the help of partners in Iraq, one expert says, meaning the offensive is a sign of a broader "Sunni uprising.”

In just one week ISIS has seized a large part of northern Iraq, including the cities of Mosul and Tikrit. Previously the group had seized large parts of Syria along the Iraq border. The group wants to see the creation of a political territory, modelled as an Islamic emirate, straddling Syria and Iraq.

But Kamran Bokhari, vice-president of Middle East affairs from Stratfor Global Intelligence, says that ISIS has only been able to advance in Iraq with support from local Sunni Muslims. He notes that the group, which he estimates has between 4,000 – 5,000 members, depends on this support.

"Four thousand to 5,000 militiamen cannot take a city -- Mosul in this case -- a city of over 2 million people by themselves,” Bokhari told CTV’s Power Play. “That’s quite an undertaking and it’s not possible physically, so they have to have support, and it seems like they’ve been at it for quite a while.”

Bokhari says the group has been aligning itself with Sunni tribes who have been “resenting Shiite domination and the marginalization of the Sunni community.”

Over the weekend, the group posted graphic images online appearing to show their gunmen executing captured Iraqi soldiers.

An Iraqi military spokesperson confirmed the authenticity of the photos, estimating that about 170 soldiers had been shot to death based on an analysis of the pictures.

But the group’s claim to have slain 1,700 soldiers could not be confirmed by the U.S.

“I’m a bit suspicious about the numbers -- 1,700 is a very high number for them to have executed. And frankly speaking, we don’t have evidence of that high of an execution toll,” Bokhari said. “But definitely, their brutality is no secret.”

Bokhari said ISIS is showing just how far it's willing to go to achieve its goal of establishing an Islamic state. "It is willing to go to any length to accomplish that and it's not just intent, they've shown capability as well," he said.

Canada’s response

After the group’s photos were posted online, Canada's acting charge d'affaires left Iraq. A spokesperson from the Department of Foreign Affairs said Canada would now be re-assessing its diplomatic presence in the country on a daily basis. Staff from the U.S. embassy in Iraq have also been forced to leave amid the worsening security situation.

Foreign Affairs Minister John Baird has condemned ISIS, labelling them a "brutal terrorist entity" that is threatening the peace and security of the region.

"Canada reiterates its condemnation of the so-called Islamic State of Iraq and the Levant, a brutal terrorist entity that is corrosive to peace and security in the region," he said in a statement.

"(ISIS) is responsible for death, destruction and brutalities in both Syria and Iraq, wreaking havoc in what is now one of the most volatile border regions on earth."

The Department of Foreign Affairs said that Canada has not been asked to provide military assistance to the region and is not considering doing so.

Meanwhile, the U.S. military has sent an aircraft carrier to the Persian Gulf as it considers its military options to help thwart the insurgency. This follows a vow from President Barack Obama last week that the U.S. would not be sending ground troops back to Iraq.

Bokhari said that the U.S. has reacted so swiftly to ISIS partly because it doesn't want it to look like the U.S.-led intervention in Iraq was a failure. He noted that it's a "slippery slope" if ISIS is allowed to advance in Iraq, and the U.S. cannot let it appear that the security situation is spiralling out of control.

Bokhari says he also believes that that the U.S. could form an alliance with Iran to counter ISIS.

“The United States and Iran worked together to topple the Taliban regime post-911, and then they co-ordinated when Saddam Hussein’s regime was being toppled,” Bokhari said. “If they did that when they were enemies and had a lot of problems, think about what could happen when relations are actually improving.”

Rising gas prices

One of the effects of the conflict that Canadians have already started to feel is a hike in gas prices.

The turmoil in Iraq has been driving gas prices to record highs across the country.

On Monday, the price for a litre of gas in Toronto reached an average of 141.9 cents a litre, according to the website Tomorrow's Gas Price Today. One year ago, the average price per litre was 129.7 cents.

Website co-founder Dan McTeague said the prices could climb even higher, due to the uncertainty over Iraq's oil supplies amid the unrest. He noted however, that gas prices have little to do with oil shortages or increased demand, and are based off of speculation.

"I think it's overreaction to a circumstance in which there's been no proof of any sort of disruption of supply," he said over the weekend.

Bokhari agrees, noting that he believes the prices will initially spike and eventually begin to taper off again, until something else happens in the region.