President Obama on Friday condemned an attack on United Nations workers in northern Afghanistan that killed at least eight, two of which were beheaded.

The attack, according to Reuters, occurred in the town of Mazar-i-Sharif following a demonstration against a Quran burning supervised by Florida pastor Terry Jones.

"I condemn in the strongest possible terms the attack on the United Nations Assistance Mission in Afghanistan today," said Obama in a statement. "We stress the importance of calm and urge all parties to reject violence and resolve differences through dialogue."

The protest reportedly drew more than 1,000 people after Friday prayers, but the event turned violent as a smaller group attacked the United Nations facility in the city.

The attack left the chief of the U.N. mission wounded. The dead included workers from Norway, Romania and Sweden, Reuters reported.