A suicide bombing in Pakistan's biggest city of Karachi has killed at least four people and wounded more than a dozen others. Officials say the bomber targeted a senior police official who was travelling in a security patrol in the garrison area of Malir. The Pakistani Taliban have said they carried out the attack. The official, Rao Anwar, was unhurt in the explosion. He said that he had received threats to his life. "The attack was against me. I was moving with my squad in Malir district when the explosion took place. I am unhurt, but some of my men have been injured," police official Rao Anwar told the AFP news agency. Karachi has long suffered outbreaks of violence, either carried out by the Taliban or because of turf wars between rival political groups. At least 800 people died in politically motivated attacks in the city last year. About 300 people have been killed so far in 2012. The security forces in August suggested that an influx of hundreds of thousands of ethnic Pashtuns - who traditionally provide the Taliban's bedrock support - had worsened tensions.