The description of events - which led to NATO pulling all its advisers out of Afghan government ministries - came amid renewed violence in a sixth day of anti-American demonstrations.

A protester was killed and seven U.S. soldiers were wounded in a grenade attack on their base as France announced its Kabul embassy was temporarily withdrawing all its civilian mentors and advisers from Afghan institutions for "safety reasons."

Germany also said it had withdrawn its national and international staff from Afghan ministries as a "precautionary measure."

Describing the sequence of events that led to the interior ministry shootings, the source said the U.S. advisers were "scolding the protesters and calling them bad names," as they watched videos of protests in Kabul.

"They called the Koran a bad book in the presence of (an Afghan colleague). After all this the guy had verbal arguments with the advisers and was threatened by them. He gets angry and shoots them. Eight rounds were fired at them," the source added, requesting anonymity.

"He then sneaks out and disappears. No one knew about the incident for more than an hour because the room is soundproofed," he said.

Asked about this description of events in the ministry on Saturday, a spokesman for NATO's U.S.-led International Security Assistance Force said: "The investigation is ongoing."

Government sources said police were hunting for an Afghan intelligence official suspected of killing the two Americans, while the interior ministry confirmed that "the suspect is one of the employees of the ministry and he is at large."

Local television quoted a source which named the suspect as 25-year-old Abdul Saboor, who had studied in Pakistan and joined the ministry as a driver in 2007 before being promoted.

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