Pakistani Taliban, whose intermediaries are currently holding peace talks with the government, Thursday claimed responsibility for an attack on police vehicles in Karachi that killed at least 12 police officers and injured dozens others. The bomb hit a police bus and van when they were heading for duties. The Taliban spokesman, Shahidullah Shahid, said the attack was aimed at taking revenge of Taliban members who have been killed in Karachi and other cities in recent days by the police and Rangers. "Or 20 members have been killed in fake encounters in a month," Shahid said in a statement. "As there is no formal ceasefire, the Taliban will carry out attacks in defence. We have the right to take such steps." He called for immediately steps taken to stop such acts by the government as it is a must for the success of dialogue process. Negotiators from the Taliban and the government have been involved in talks for two weeks to find out a solution to the problem. Both sides have not yet agreed on a ceasefire despite calls from different segment of society.