Hundreds of Afghans clashed with police and security forces for a second day of angry protests aimed at NATO troops who improperly disposed of copies of the Quran.

Several hundred protesters threw stones at police and shouted “Death to America” during a demonstration Wednesday outside Kabul while another demonstration was held in a different part of the capital.

The French news agency reports that three people were injured when security forces fired on protesters attempting to march to the center of the city.

The U.S. embassy announced it has placed its staff on lockdown and suspended all travel.

Separate protests were also reported in other parts of the country including the eastern city of Jalalabad, where the crowd reportedly blocked the main highway.

The commander of the international coalition, U.S. General John Allen, on Tuesday issued an apology and ordered an investigation into a report that coalition forces “improperly disposed” of a large number of Islamic religious texts, including the Quran.

“I assure you…I promise you…this was not intentional in any way. 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 circumstances surrounding the alleged desecration are unclear. Unconfirmed reports suggest that NATO troops attempted to dispose of a load of Qurans by setting them on fire, but were stopped by Afghan employees at the base.

Afghan protests against the destruction of the Muslim holy book have turned deadly in recent years. In April 2011, about 20 people were killed during several days of protests across Afghanistan after little-known U.S. pastor Terry Jones burned a Quran at his small Florida church.