Seven Afghan children were killed when a bomb went off in western province of Ghor, a provincial government spokesman said. "A total of seven innocent children were grazing their animals in Taiwara district but one stepped on a pressure- plate bomb leading to a powerful blast killing all of them on the spot," Abdul Hai Khatibi said. He blamed Taliban insurgents for planting the bomb targeting security forces in the area. Taliban militants, who launched an annual spring offensive on May 3 against Afghan and NATO forces, have been largely relying on roadside bombs and suicide attacks, often causing civilian casualties. A total of 3,021 Afghan civilians were killed in the conflict in 2011, up 8 percent compared with 2010, according to the United Nations annual report released in Kabul in February this year.