Six NATO service members were killed on Sunday in an insurgent attack in southern Afghanistan, the international alliance said in a statement.

NATO did not give further details, in keeping with a policy of waiting for individual countries from the alliance to identify their casualties.

Most NATO troops in southern Afghanistan come from the United States, but there are contingents from several nations in the area.

Fighting has increased in southern Afghanistan as a surge of U.S. troops have poured into Helmand and Kandahar provinces this year in an attempt to push the Taliban out of their traditional strongholds.

Sunday's attack was the second incident in two weeks to kill so many service members.