Fourteen Americans were killed in helicopter accidents in Afghanistan on Monday, marking one of the deadliest days since the U.S. entered the fight.

In the first accident, a chopper crashed in the west of Afghanistan after leaving the scene of a battle with insurgents. Ten Americans were killed in that crash, including seven soldiers and three agents with the U.S. Drug Enforcement Administration.

DEA agents often accompany U.S. troops in Afghanistan because the country is the world's major source for opium. Since the mission began, NATO has struggled to curb production of the drug, which helps finance the Taliban.

Another 26 people were injured in the crash, including 11 U.S. military personnel, one civilian, and 14 Afghan soldiers. No cause has yet been given for the accident.

In another accident that occurred in southern Afghanistan, two helicopters crashed in mid-air. Four troops were killed and two were wounded in that crash.

Hostile fire has been ruled out by the U.S. in the southern Afghan crash, but no other reason for the accident has been released.

According to a purported Taliban spokesperson, insurgents shot down a chopper in the northwest, but the claim has not yet been verified nor confirmed to be one of the deadly Monday crashes.

The deaths come as U.S. President Barack Obama considers a request for up to 80,000 more troops from his Afghanistan military commander, Gen. Stanley McChrystal.

So far in October alone, 46 U.S. soldiers have been killed in Afghanistan.

The high price of the war in recent days is likely to further affect the plummeting popularity of the mission -- and raise further security concerns about the presidential runoff election scheduled for Nov. 7.

The runoff comes after evidence of widespread fraud, and the decision to cancel thousands of ballots in favour of President Hamid Karzai, rendered his victory invalid.

It is widely hoped that the runoff will produce a result that will satisfy Afghans as fair and legitimate -- an outcome that could be the key factor in whether the U.S. ramps up its troop commitment.

Abdullah Abdullah, the lead challenger for Karzai's job, has set out a number of demands for the runoff election:

  • The firing of anyone implicated in fraud;
  • The suspension of minister he claimed had been campaigning for Karzai before the official campaign period began on Sunday.

He didn't say, however, what he would do if the demands aren't met.

"I reserve my reaction if we are faced with that unfortunate situation," he said.

Canada's military roll in Afghanistan is scheduled to end in 2011. In total, 131 Canadian soldiers have been killed in Afghanistan.

A Canadian diplomat and two Canadian aid workers have also been killed over the course of the insurgency.