LONDON, April 10 (IslamOnline.net & News Agencies) - The pro-U.S. Iraqi Shiite leader Abdul Majid al-Khoei was assassinated Thursday, April 10, in the Shiite holy city of An-Najaf in central Iraq, spokesman for the London-based al-Khoei foundation Fadhel Milani confirmed.

Assailants armed with knives attacked al-Khoei inside Imam Ali Mosque in An-Najaf - one of the holiest sites for Shiite Muslims, Fadhel Milani told BBC News Online.

Milani said Sheikh al-Khoei had been in the mosque with four friends when he noticed another cleric, Haydar Kilidar, was coming under attack.

"Al-Khoei attempted to protect Sheikh Kilidar but was himself attacked by the crowd," Milani told the BBC.

"Persons who were with him... said he was martyred by treacherous hands," Agence-France Presse (AFP) quoted his nephew Jawad al-Khoei as saying.

"The people gave him a very warm welcome when he entered the mosque and were happy that he has come home to help them," Moaed Fayyad, a journalist in An-Najaf, who was accompanying Sheikh al-Khoei, told Al-Jazeera satellite channel.

"All of a sudden an angry mob armed with knives and swords stormed the mosque and stabbed al-Khoei to death…they were dying for his blood," he said.

Majid was the son of the late Ayatollah al-Khoei, one of the main leaders of Iraq's Shiite community during the 1991 Gulf War, who died in 1992 while under house arrest.

There had been speculation that al-Khoei, who repeatedly called for Shiite cooperation with the United States, had gone back to An-Najaf two weeks ago from London with help from U.S. forces, AFP said.

His return signaled a U.S. attempt to promote a "pro-American" current as Saddam Hussein's regime collapses.

Milani said he believed Sheikh al-Khoei's association with the occupation forces had provoked the attack, saying "certain people did not want him in that role".

He said other colleagues from London would now "think twice" before returning to Iraq.

U.S., U.K. Condemn Attack

The White House, for its part, said Thursday it "strongly condemns" the assassination of al-Khoei.

"The very regrettable assassination of a sheikh from An-Najaf -- which the United States strongly condemns, and we express our sympathies to the people of An-Najaf over this assassination -- is another reminder of how dangerous the situation is inside Iraq," said White House Spokesman Ari Fleischer.

British Foreign Secretary Jack Straw also lamented al-Khoei’s killing.

"I knew Sheikh al-Khoei. He was resident in this country. He had huge expectations about the future of the Shiia people post-Saddam," Straw said at a press conference with Kuwait's State Minister of Foreign Affairs Mohamed Sabah al-Salem al-Sabah.