Pakistan was plunged into a shock on Tuesday after the assassination of Governor of Pakistan's biggest province of Punjab, Salman Taseer.

Arrested Pakistani police guard Mumtaz Qadri, who claimed that he killed Pakistan's Punjab Governor Salman Taseer, sits in a police van near the assassination site in Islamabad, capital of Pakistan, on Jan. 4, 2011. Pakistan's Punjab Governor Salman Taseer was assassinated by his bodyguard Tuesday afternoon at a market in the downtown area of the country's capital Islamabad, reported local media. [Sadia/Xinhua]

A guard from the anti-terror Elite Force fired at the Governor in the Islamabad's posh Kohsar Market shortly after he had luncheon at a restaurant, according to the Interior Minister Rehman Malik.

Guard Malik Mumtaz Hussain, who later surrendered to police, said he shot the governor dead as he had opposed an Islamic law which carries death penalty for those who show disrespect to the Prophets of Islam.

The ruling Pakistan People's Party declared a two-week mourning and the Prime Minister announced three-day national mourning to pay homage to the slain governor.

The President and the Prime Minister cancelled all their official engagements and the Interior Minister Rehman Malik would himself head the investigation.

Malik said that the attacker told the investigators that he killed the governor as he had "insulted" the religion.

Pakistani President Asif Ali Zardari strongly condemned the assassination of Governor Punjab Salman Taseer and directed Malik to personally supervise the investigations and report to him urgently, the presidential spokesman said.

Spokesperson said that the President was informed about the tragic assassination during a meeting of the party's lawmakers in Karachi after which all the meetings scheduled for Tuesday were postponed to a later date.

The Prime Minister has ordered for a high level inquiry into the incident and submit the report at the earliest. The culprits involved in the assassination, he said would be brought to justice.

Gilani appealed to the workers and supporters of his party to remain calm so that proper investigation could be conducted.