In his letter, according to Mr. Karzai’s press office, Mr. Obama wrote: “I wish to express my deep regret for the reported incident. I extend to you and the Afghan people my sincere apologies.”
Earlier-
“I offer my sincere apologies for any offense this may have caused, to the president of Afghanistan, the government of the Islamic Republic of Afghanistan and, most importantly, to the noble people of Afghanistan,” the NATO commanding general, John R. Allen, said in a statement that was recorded and sent to local television and radio networks here, explaining that the burnings had been unintentional.
To know details about the violent incident please visit the following links:
http://www.nytimes.com/2012/02/24/world/asia/koran-burning-afghanistan-demonstrations.html
http://www.bbc.co.uk/news/world-asia-17152705
http://www.timeslive.co.za/world/2012/02/24/obama-apologises-as-afghan-koran-protests-rage