Sri Lankan President Chandrika Kumaratunga declared a state of emergency Saturday after Foreign Minister Lakshman Kadirgamar was assassinated.
The state of emergency was declared to ensure national security and "facilitate enhanced security measures and effective investigations of this act of wanton terror," a presidential spokesman said.
Kadirgamar was shot at around 11:15 p.m. local time Friday (1715 GMT) and passed away at 00:15 a.m. Saturday (1815 GMT Friday).
Security sources said a sniper shot at him while he was near the swimming pool of his private residence in the plush residential area of Cinnamon Gardens in the capital Colombo.
Kadirgamar was admitted to Colombo's national hospital and succumbed to serious head injuries.
The roar of helicopters is being heard in Colombo. Police said Sri Lankan armed forces have launched a helicopter search for assailants.
All roads in Colombo 7 area, where Kadirgamar's highly guarded residence is located, remain blocked by armed forces.
While condemning this act of terror, Kumaratunga stated in a statement that her government will not be bowed by such heinous acts of violence and will spare no effort to bring the perpetrators of this dastardly act to justice.
During the 11-year tenure of his leadership of Sri Lankan foreign policy, the nation achieved incomparable success in its international relations, which culminated in the LTTE being proscribed in many foreign countries, said Kumaratunga.
Kumaratunga said he was a hero of our times, and he waged a relentless struggle against terrorism in all its forms, despite continuous threats to his life.
UN Secretary-General Kofi Annan condemned in a statement the slaying of Kadirgamar, labeling it as a "criminal and senseless act."
"He deplores in the strongest terms this criminal and senseless act and hopes that the perpetrators will be found and brought to justice," the statement said.
"Sri Lanka has lost a deeply respected statesman dedicated to peace and national unity. The secretary-general hopes that this tragedy will not weaken the commitment of the people of Sri Lanka to achieve a durable peace in the country," it added.
US Secretary of State Condoleezza Rice strongly condemned the assassination of Kadirgamar and offered condolences to his family and friends.
"I am shocked and saddened by the assassination of Sri Lankan Foreign Minister Lakshman Kadirgamar. This senseless murder was a vicious act of terror, which the United States strongly condemns. Those responsible must be brought to justice," Rice said in a statement.
Kadirgamar, a Tamil, was in the forefront of Sri Lankan government's campaign for an international ban on the Liberation Tigers of Tamil Eelam (LTTE) rebels.
As a well known lawyer, Kadirgamar entered politics in 1994 and was immediately made the foreign minister.
He held the post from 1994 to date, barring a short period between 2001 and 2003.
Kadirgamar figured high on the Tamil Tigers' hit list and was provided with elite commando security.