QUETTA, Pakistan -- Black flags flew over the sprawling family home of Aimal Kasi on Friday as relatives and friends mourned the convicted killer's execution in Virginia.

Police were out in force in his hometown and security was increased at U.S. and international installations in Pakistan, but the streets were mostly quiet.

Kasi was put to death by lethal injection Thursday at a prison in Virginia for murdering two CIA employees in 1993. He has said he carried out the killings to protest America's policies toward the Muslim world.

The State Department has warned his execution could lead to retaliation against Americans, despite a plea for peace from Kasi's family, and from the condemned man himself. Four Americans were killed in Pakistan after Kasi's 1997 conviction.

U.S. actions condemned

Pakistani religious leaders were quick to praise Kasi and condemn the United States for his execution.

"The sacrifice of Aimal Kasi will create a spirit of revolution among Muslim youth in the entire world," said Maulana Noor Mohammed of the extremist Jamiat Ulema-e-Islam party. "The revolution will be against America. Hatred against America will increase."

The execution prompted heightened security, already ramped up after a series of attacks on Westerners since President Pervez Musharraf threw his support behind the U.S.-led war on terrorism that began after the Sept. 11 attacks on the United States.

The U.S. Embassy and American consulates in Pakistan closed early Friday. Other embassies and international organizations in Pakistan said they also were taking precautions.