A blast has hit a mosque in Kandahar during a memorial service for the assassinated half-brother of Afghan President Hamid Karzai, officials say. The explosion killed four people, including the top cleric of the provincial council. Some reports suggest it was a suicide bomb, but this has not been confirmed. Ahmad Wali Karzai, a controversial but key figure in Natos battle against the Taliban, was gunned down at home by his bodyguard on Tuesday. It was a suicide bombing. It was inside the mosque, a member of Kandahars provincial council was quoted as saying by the media. The service was about the end when it happened, the official added. No group has so far admitted carrying out the attack.