Seven people were killed in Afghanistan on Wednesday during protests over the burning of the Koran at a NATO base near Kabul.

Demonstrators and state security forces clashed for the second day in a number of cities in the country. Police fired rubber bullets at protestors who were wielding rocks and sticks. At least six people were killed in Kabul, while another protestor was killed in the city of Jalalabad, where 11 fuel tankers were set on fire by angry citizens.

Western contractors reportedly opened fire on protestors and are responsible for some of the deaths.

“As a result of shooting at protesters by foreign guards at Camp Phoenix, one person was killed and 10 others were wounded,” the Afghan interior ministry told the Financial Times.

Afghan President Hamid Karzai is urging calm, but has also condemned the Koran burning.

Protests are the right of people but I ask my countrymen to avoid violence, he said in a statement.

U.S. military officials have opened an investigation into the discovery of charred Korans at NATO's main base in the country. Reports vary on the extent of the desecration of the Islamic holy book. Some reports say that four copies of the Koran were either damaged or burnt, but the Afghan officials who visited the base said at least 10 Korans were purposefully set on fire.

However, The Wall Street Journal reported that NATO coalition soldiers tried to burn a truckload of Korans and other religious items at Bagram Air Field on Monday because they were considered to be extremist literature and clandestine communications being used and shared by prisoners.

It was not a decision that was made with respect to the faith of Islam. It was a mistake. It was an error. The moment we found out about it we immediately stopped and we intervened, NATO commander General John Allen told reporters of the incident.

The incident has sparked a wave of anti-American and anti-West protests and sentiments across Afghanistan at a crucial time when NATO members are preparing to pull troops out of the country. Protestors were heard chanting Taliban slogans and Death to America, while others called for violent retaliation.

The American embassy was put on lock-down and staff members have been told not to travel. The United States has apologized for the Koran burning, but it has done nothing to stop the protests.