KABUL, Afghanistan — A coalition service member was killed in an insurgent attack in southern Afghanistan, NATO announced Wednesday, as operations to flush out insurgents moved forward in the Taliban stronghold of Kandahar.

The service member was killed in a fight with insurgents in the south on Tuesday, the coalition said without giving further details. NATO generally does not announce the nationalities of troops killed until after next of kin have been contacted by the service member’s country.

This year is already the deadliest of the nine-year war, with 536 dead as of Wednesday. There are about 140,000 international forces in Afghanistan.

Southern Afghanistan remains highly volatile. The coalition is currently conducting an operation, called "Dragon Strike," to clear insurgents from areas around the city of Kandahar, in the Taliban’s heartland.

The operation has so far flushed militants out of Arghandab district, according to an Afghan army official. It has also cleared the area of mines, a major concern for residents, said Afghan army Lt. Col. Nabeullah Khan.

NATO said Wednesday that it had detained several insurgents suspected of making improvised explosive devices, and was searching for a Taliban leader they believe has led attacks on coalition forces in the area.

In the east, security officials said Pakistan has told NATO leaders it will stop protecting U.S. and NATO supply lines to Afghanistan if foreign aircraft stage further cross-border attacks against fleeing militants.

The threat was seen as mostly aimed at tamping down criticism inside Pakistan, where anti-American sentiment runs high and where conspiracy theories that the U.S. army is poised to invade the nation from bases in Afghanistan are rampant.

But it was also a sign of Pakistani unease at the attacks on Saturday and Monday by NATO aircraft against militants in its northwest tribal areas that killed more than 70 militants and a reminder of the leverage the country has in its complicated alliance with Washington.