Kabul: At least 13 persons were killed on Monday when a suicide bomber struck a bus carrying security personnel in Afghanistan's capital Kabul, officials said. "The bus was running along a busy road in Pul-e-Charkhi area at around 6.30 a.m. A terrorist rammed his explosive-laden car into the bus, causing a heavy explosion," witness Farhad Mohammadi told Xinhua news agency. "Most of the victims were foreign security guards onboard the bus. Initial information showed they were Nepalese," a security official said. Twenty-five others were injured in the attack, the official said. The Taliban militant group has claimed responsibility for the attack.