Afghan protesters shout anti-U.S. slogans during a protest against the burning of Korans by US troops
Afghan protesters shout anti-U.S. slogans during a protest at a mosque in the city of Herat.

US President Barak Obama apologised for the burning of Korans by US troops at a military base in Afghanistan.

The President sent a letter to Afghanistan's President Hamid Karzai expressing his "deep regrets", saying the incident which took place earlier this week was genuinely a mistake.

"I convey my deep sympathies and ask you and the people to accept my deep apologies," the letter explains.

Obama further said US authorities would investigate the incident and question those involved.

"The error was inadvertent; I assure you that we will take the appropriate steps to avoid any recurrence, to include holding accountable those responsible," he wrote.

Protests against the desecration entered their third day. They have mainly affected northern and eastern Afghanistan.

Many of the protesters were heard chanting "Death to the US" and "Death to Obama"

Reports suggest that up to 15 people have now died in the violence and dozens of others have been injured.

On February 23, gunmen attacked at least two military bases.

President Karzai said to members of parliament that a US officer was responsible for the burning but called for calm and said it was a result of "ignorance".

The incident also provoked a reaction from the Taliban who called on Afghans to continue protesting.

The group issued a statement urging its supporters to kill foreign troops and target military bases to "teach them a lesson that they will never again dare to insult the Holy Koran".

Koran Burning Controversy: Thousands of Afghans Protest at Nato Base

Afghanistan Koran Burning: Four Dead, 26 Injured