Afhan soldier opens fire, kills 2 U.S. troops

Two U.S. troops have been shot to death and four more wounded by an Afghan solider who turned his gun on his allies in apparent anger over the burning of Korans at a U.S. military base in Afghanistan, an Afghan official tells CBS News.

A statement from the International Security Assistance Force - Afghanistan, the international coalition in the country, confirmed that two troops were killed in Eastern Afghanistan on Thursday by "an individual wearing an Afghan National Army uniform."

ISAF does not typically give the nationality of casualties until family members have been notified, but the CBS News source in the Afghan government said those killed and injured in the attack in the Khogyani district of the eastern Ningarhar province along the border with Pakistan were Americans.

The source also said the shooting appeared to be motivated by the burning of Korans at the sprawling U.S. Bagram air base, north of Kabul, but he did not provide additional details as to what led him to that conclusion.

There have been violent anti-U.S. protests across Afghanistan since the American military on Tuesday apologized for what it said was the accidental "improper disposal" of religious materials, including Muslim holy books, at Bagram. The U.S. is cooperating with the Afghan government to investigate the incident.

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There had been reports of violent protests again on Thursday at U.S. and NATO military bases around Afghanistan, including one protest at which two protesters were apparently shot and killed by responding police.