Afghan officials say at least eight people were killed at a U.N. office in the northern city of Mazar-i-Sharif when a Quran burning protest turned violent.

Demonstrators stormed the U.N. office Friday, opening fire on guards and setting fires inside the compound after learning that a Florida pastor had burned a copy of the Muslim holy book.

NPR’s Quil Lawrence said protests broke out in several cities after Friday sermons — the first Friday since news reached Afghanistan that the preacher had burned a copy of the Muslim holy book — but the demonstrations in Mazar-i-Sharif turned violent.

Gen. Daud Daud, commander of Afghan National Police in the north, said the dead included five guards working for U.N. and two other people employed at the complex.

Daud said one other person was wounded, but a police official in Balkh province said later that the injured person, who was a foreigner, died.

Media reports citing a local official said two of those killed had been beheaded, though that could not be immediately confirmed.

Also Friday, U.S. officials said 6 American soldiers had been killed this week during an ongoing operation in Afghanistan’s northeastern province of Kunar, where Taliban fighters continue to cross over the mountainous border from Pakistan.

NPR’s Quil Lawrence reported from Kabul, Afghanistan, for theis story, which contains material from The Associated Press. Copyright 2011 National Public Radio. To see more, visit http://www.npr.org/.