To: Kenneth E. Phillipps who wrote (124556 ) 2/23/2012 9:41:08 AM From: TideGlider 2 Recommendations Respond to of 224750 Obama apologizes over Quran burning as two US troops shot dead in Afghanistan Shah Marai / AFP - Getty Images Afghans shout anti-American slogans during a protest in Kabul on Thursday. By NBC News, msnbc.com staff and news services Updated at 9:24 a.m. ET: KABUL, Afghanistan -- President Barack Obama has written a letter to his Afghan counterpart apologizing for the burning of copies of the Quran at a NATO military base in the country. Two U.S. soldiers were also shot dead Thursday at a protest about the desecration of the holy books. A man wearing an Afghan government soldier's uniform killed the American troops and wounded four others at the demonstration in Nangarhar province, officials told NBC News. There have been violent protests daily since it emerged on Tuesday that Qurans used by detainees held at the Bagram military base had been burned. The incident has become a public relations disaster for foreign forces in Afghanistan. A statement from President Hamid Karzai's office said the U.S. ambassador to Afghanistan had delivered the letter from Obama Thursday. Taliban to Afghans: Kill foreigners over Quran burnings In the letter, which is quoted in the statement, the U.S. president expressed his "deep regret for the reported incident" and offered his "sincere apologies." According to the statement, Obama wrote: "The error was inadvertent; I assure you that we will take the appropriate steps to avoid any recurrence, to include holding accountable those responsible." Tommy Vietor, a spokesman for the National Security Council, told NBC News that Obama had "expressed our regret and apologies over the incident in which religious materials were unintentionally mishandled at Bagram air base." Riots triggered by the inadvertent Quran burning at a U.S. military base prompted the U.S. to lock down its embassy. NBC's Atia Abawi reports. The Quran burnings at the vast Bagram base could make it even more difficult for U.S.-led NATO forces to win the hearts and minds of Afghans and bring the Taliban to the negotiating table ahead of the withdrawal of foreign combat troops by the end of 2014. Muslims consider the Quran the literal word of God and treat each book with deep reverence. Desecration is considered one of the worst forms of blasphemy. According to Haji Mohammad Hassan, the deputy police of Khogayani district in Nangarhar province, American soldiers had starting firing at protesters who were attacking their base. He said that an Afghan soldier then turned his weapon on them, shooting six, killing two and injuring four. PhotoBlog: 'Death to America!' Afghan anger over Quran burning intensifies Hassan said the Afghan soldier escaped by joining the crowd of protesters. However, a provincial official from Nangarhar province, who asked not to be named, said the shooter had been killed after the attack. The Taliban have claimed responsibility for the attack, NBC News reported. Taliban spokesman Zabiullah Mujahid said in a text message that they infiltrated the army with one of their fighters who had shot and killed the Americans. Mujahid claims their fighter killed 10 Americans. More from msnbc.com and NBC News: