Afghan officials said at least twelve people have been killed at a UN operational centre in the northern city of Mazar-i-Sharif when protest against the burning of the Quran turned violent.

Demonstrators stormed the UN office Friday, opening fire on guards and setting fires inside the compound after reports that a evangelical pastor burned a copy of the Muslim holy book in Florida in March.

At least eight foreigners and four Afghan protesters have been killed when the demonstration turned violent. An estimated 20 other demonstrators were injured.

Two of the UN staff members were beheaded, according to police.