Gunmen have carried out more attacks in the southern Pakistani city of Karachi and across Sindh province following the killing of a leading local politician.
The number of those killed in rioting that followed the killing of Raza Haider rose to 53 on Tuesday. Scores more have been wounded.
Leaders of Mr Haider's MQM party have renewed their appeals for calm.
Mr Haider was shot dead in a mosque along with his guard. PM Yousuf Raza Gilani has ordered an inquiry.
In Hyderabad - Karachi's neighbouring city - gunmen opened fire on a train heading for the eastern city of Lahore, officials said.
The driver was injured and the engine was destroyed in the attack, police said.
The BBC's Syed Shoaib Hasan in Karachi said MQM leaders had started to backtrack on earlier claims that the ANP political party had been behind Monday's killings.
In a press conference they said the attack could also be due to their party's strong stance against the Taliban and other militant Islamic groups.
Most of those killed were from the Pashtun community, which dominates the ANP.
However, the ANP said that only two of its activists were among the dead.