A gunman wearing an Afghan army uniform on Sunday shot and killed a member of the U.S.-led coalition forces fighting in Afghanistan -- the latest in a spate of insider attacks that are fracturing the trust between NATO and Afghan forces.

Separately, officials said 11 Afghan civilians were killed by land mines on Sunday in explosions in the east and south.

U.S. Army Maj. Martyn Crighton, a spokesman for the coalition, said the service member was killed in the south. His identity and nationality were not disclosed.

Mohammad Zarak, spokesman for the governor of Helmand province, said the shooting took place in Nad Ali district after an argument between an Afghan soldier and coalition service members.

Coalition figures show at least 60 coalition service members have been killed so far this year and others have been wounded in about 45 insider attacks, where members of the Afghan security forces or insurgents dressed in their uniforms turn their guns on U.S. and allied troops.

The insider attacks have raised questions about how effectively the allied forces can train the Afghans to take over security of their own country in 2014 and beyond. Foreign forces are due to turn over security responsibility to the local military by the end of 2014.

A roadside bomb killed three men, two women and a baby in Khost province of eastern Afghanistan, deputy provincial police chief Youqib Khan said. He said their vehicle hit the bomb as they were returning from a hospital.

Three other civilians were killed when their vehicle detonated a land mine on the road between Helmand and Kandahar provinces, a government statement said.

Also in the south, two civilians who were walking were killed by a land mine in Khakrez district of Kandahar province, said Ahmad Jawed Faisal, a spokesman for the provincial governor.

The United Nations says homemade bombs continue to be the weapons that kill the most civilians in the war.