Roadside bombs struck Afghan security forces in two separate incidents, killing seven people and wounding five, officials said Wednesday. Three Afghan soldiers were killed and four wounded when their vehicle was hit by a roadside bomb Wednesday in the Musa Qala district of northern Helmand province, said Gen. Mohammad Zahir Azimi, the Defense Ministry spokesman. US, British and Afghan troops pushed the Taliban out of Musa Qala late last year after the militants overran the area in early 2007 and held it for 10 months. Musa Qala lies at the heart of the country's opium poppy-producing region. In eastern Khost province, meanwhile, four Afghan guards working for the US military were killed when their vehicle was struck by a roadside bomb Tuesday, said Wazir Pacha, a spokesman for the provincial police chief. Another guard was wounded in the blast in the Shinkay district, he said.