An Afghan city mayor was killed Tuesday when a bomb ripped through his vehicle as he travelled home from work in the east of the country, police said. "The mayor has been killed. Two of his nephews and two civilians were wounded in the blast," Khost province police chief Abdul Qayom Baqizoi said. The mayor, Sakhi Amirullah Amiri, was attacked as he was heading home from work in the city of Khost. The bomb blew up the vehicle in which he was travelling. Provincial public health director Amir Badshah said that one of the mayor's nephews was in critical condition. There was no immediate claim of responsibility. Khost, which is on the border with Pakistan, has been hammered by a series of attacks claimed by extremist Taliban insurgents.