(MSNBC) KABUL, Afghanistan — Barack Obama has written a letter formally apologizing for the burning of copies of the Quran at a coalition military base in Afghanistan, the Afghan president’s office said Thursday, amid reports that two American troops had been shot dead.

A man dressed as an Afghan government soldier killed the soldiers and wounded four others during a protest about the burning of Islamic holy books that had been used by detainees held at the Bagram military base, a police officer and a provincial Afghan official told NBC News.

There have been violent protests every day since the news of the Quran desecrations emerged on Tuesday in what has become a public relations disaster for foreign forces in Afghanistan.

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