A roadside bomb blast killed four Afghan civilians in the western province of Herat on Monday morning, while a similar attack killed two private security guards in the eastern region, officials said. A truck was blown up by the roadside bomb in the Meyan Band area of Adraskan district of Herat province. It was carrying labourers to a construction project, said Abdul Raouf Ahmadi, spokesman for the western region police. Four workers were killed and three others were wounded, Ahmadi said. He blamed the attack on Taliban insurgents. In a separate roadside blast Monday morning, two private security guards working with a construction company were killed and one other was wounded in Bak district of the south-eastern province of Khost, said Lutfullah Babakarkhel, the district administrative chief. Taliban spokesman Zabiullah Mujahid claimed responsibility for the attack and claimed five security guards were killed in the explosion.