KABUL, Afghanistan – An explosion targeting international troops on a foot patrol in southern Afghanistan killed three members of the U.S.-led coalition Thursday, the coalition said.

The coalition did not release any details about the attack, including the troops' nationalities or the location of the blast. American forces make up the vast majority of the coalition, which includes special forces units and soldiers who train Afghan army and police forces. The 40-nation NATO-led force operates under a separate command.

Southern Afghanistan is the center of the Taliban-led insurgency. The last three months have been the deadliest for international troops in Afghanistan since the 2001 U.S. led invasion.

A record number of U.S. and NATO troops are in Afghanistan – around 65,000 – exposing more soldiers than ever to increasingly lethal Taliban bombings and ambushes.

More than 3,200 people have died in violence countrywide so far this year, according to an Associated Press tally of figures provided by Afghan and Western officials.

At least 93 U.S. troops have died in Afghanistan this year, a pace that would make 2008 the deadliest for American forces since the 2001 invasion. At least 29 British troops have died, as have at least 15 Canadian forces.