At least four people were killed when thousands of protesters surrounded a UN compound in the northern Afghan city of Konduz to condemn the recent burning of Korans at a NATO base.
A health department director in Konduz, Dr. Saad Mukhtar, said local hospitals had reported four dead and some 50 others injured in the violence.
Other sources were citing as many as seven deaths as the UN facility was ablaze.
Police spokesman Sarwar Husaini said officers managed to stop protesters from entering the UN compound and that reinforcements had been sent to protect the complex.
He also said protesters burned cars and shops in Konduz. Witnesses described columns of smoke hanging over parts of the city.
NATO Recall After Ministry Killings
The protest violence was accompanied by a report that NATO was recalling all its staff working at ministries in the Afghan capital after two U.S. officers were shot dead inside the Interior Ministry.
NATO's top commander in Afghanistan, General John Allen, said that for "protection reasons" he has taken "immediate measures" to recall staff.
NATO said in a statement that two of its service members were killed on February 25, without revealing their nationalities. But Western news media quoted Afghan officials as saying privately that two American advisers were killed.
The Afghan Taliban claimed responsibility for the killings, saying they were in retaliation for the Koran burnings.
The Taliban have urged all Afghans to retaliate with violence against foreign troops.
February 25 marked the fifth day of demonstrations over what U.S. officials say was the mistaken burning of copies of the Islamic holy book, for which President Barack Obama and others have apologized.
There were continuing protests in at least four provinces of Afghanistan over the incineration of Korans -- which prisoners were allegedly using to pass messages -- at the U.S. air base at Bagram near Kabul.
In Laghman Province, police chief Abdul Rahman Sarjang said some 1,000 protesters gathered in Mihtarlam for what began as a peaceful demonstration. But the protesters soon started throwing stones at police and then tried to attack the governor's residence.
Hospital officials told AFP that 15 protesters had been brought in with gunshot wounds from the unrest there.
Government and local police sources said rallies in the eastern provinces of Logar and Nangarhar, and the central province of Sari Pul, were largely peaceful.
An angry crowd at a protest in Paktika Province this week over the Koran burnings
Reports of the Koran burnings -- which came to light after workers discovered charred copies of the Islamic holy book among refuse -- have sparked Afghan protests in which at least 21 people had been killed through February 24.
President Hamid Karzai's government and the U.S.-led NATO mission in Afghanistan have appealed for calm and restraint, fearful that Taliban insurgents are trying to exploit the anti-American backlash.
U.S. President Obama sent a letter of apology to Karzai, saying the incident was a mistake and vowing to hold accountable whoever was responsible. U.S. authorities had already announced an investigation into the incinerations.
Karzai has blamed a U.S. military officer.
Based on AP and AFP reporting