Kabul, Feb 24 (IANS): At least 15 people have died in violence over the past three days in Afghanistan following reports of burning holy Quran by foreign soldiers.

Afghans in various provinces staged demonstrations that entered its third day Thursday. At least 15 people died and dozens of others were injured in clashes with police, Xinhua reported.

The protests erupted Tuesday in Bagram, the main US military base 50 km from Kabul, after media reports said copies of the Quran were found in the rubbish that NATO transported in a truck the previous night to a pit where waste is burned.

Protests have since swept across the country.

US President Barack Obama Thursday apologized over the incident, the Afghan presidency said in a statement. In a letter to President Hamid Karzai, Obama said the incident was not intentional and assured him of full investigation, it said.

Karzai has appealed for calm and urged the Afghans "not to resort to violence".