The U.S. military in Afghanistan has confirmed the deaths of two civilians during an operation against insurgents in eastern Khost province.

A statement by the U.S.-led coalition said troops came under fire while searching compounds for militants suspected of carrying out bombings and smuggling weapons.  The U.S. military said troops returned fire, killing several insurgents and a woman and a boy who were inside a building from which the militants were shooting.

But residents and local Afghan officials say six civilians from the same family -- three men, two children and a woman -- were killed during the raid.

A crowd of angry villagers gathered and shouted anti-U.S. slogans after the incident.

Civilian casualties are a deeply sensitive issue in Afghanistan, where more than 55,000 NATO and U.S. troops are on the ground to fight a resurgent Taliban movement and help reconstruction efforts. 

Afghan President Hamid Karzai has repeatedly called on the U.S. military and NATO to reduce civilian causalities.  U.S. and NATO officials have said they are doing all they can and have put some of the blame on the Taliban and other insurgents who they say use Afghan civilians as human shields.

On Tuesday, lawmakers and residents in southern Helmand province said a NATO airstrike killed more than 30 people, including civilians. 

NATO denied any civilians deaths, but said 12 Taliban insurgents were killed.

Some information for this report was provided by AFP, AP and Reuters.