US President Barack Obama has sent a letter to the Afghan President Hamid Karzai apologising for the burning of copies of the Koran at a US military base.
"I wish to express my deep regret for the reported incident," Mr Obama wrote in the letter. "I extend to you and the Afghan people my sincere apologies.
"The error was inadvertent; I assure you that we will take the appropriate steps to avoid any recurrence, to include holding accountable those responsible."
The letter was presented to President Karzai by US ambassador Ryan Crocker.
The incident at the US military base at Bagram north of Kabul sparked three days of fierce anti-US protests in which at least 12 protesters were killed.
Two US soldiers also died when an Afghan army colleague turned his weapon on them as demonstrators approached a US base in eastern Nangarhar province, the military and officials said.
According to a district chief in the province, Mohammad Hassan then escaped among the crowd while two protesters were killed and six wounded when the foreign soldiers returned fire.
The President’s office said that Mr Karzai told members of parliament that a US officer was responsible for the burning that was done "out of ignorance".
The Organisation of Islamic Cooperation denounced the incident as a "deplorable act of incitement."
