Pakistan is on high alert ahead of the funeral of Punjab governor Salam Taseer, who was assassinated in the capital, Islamabad, on Tuesday. Taseer was shot dead by one of his own bodyguards outraged by his opposition to blasphemy laws carrying the death sentence for insulting the Muslim faith.
One of Taseer's bodyguards, Malik Mumtaz Hussein Qadri, was detained immediately after the shooting at Kohsar Market in Islamabad. He has confessed to the murder, according to Pakistan's interior minister, Rehman Malik.
"We will investigate whether it was an individual act or there is some organisation behind it," Mr Malik told a news conference.
US Secretary of State Hillary Clinton called Taseer's death a "great loss".
"I had the opportunity to meet Governor Taseer in Pakistan and I admired his work to promote tolerance and the education of Pakistan's future generations," said Clinton in a statement.
The Pakistani prime minister, Yousuf Raza Gilani, declared three days of national mourning and appealed for calm.