Up to 20 U.N. staff killed in north Afghan city

Afghan protesters angered by the burning of a Koran by a U.S. pastor killed up to 20 U.N. staff, beheading two foreigners, when they over-ran a compound in a normally peaceful northern city on Friday in the worst ever attack on the U.N. in Afghanistan.

At least eight foreigners were among the dead after attackers took out security guards, burned parts of the compound and climbed up blast walls to topple a guard tower, said Lal Mohammad Ahmadzai, a police spokesman for the northern region.

Afghan police and army, who the United Nations rely on for their first line of defense, were apparently unable to control the crowd. German troops are also stationed in Balkh, and the NATO-led coalition said they had received a request for help.

"Eight foreigners were killed, and two were beheaded," said Ahmadzai.

A United Nations spokesman confirmed employees had been killed but declined to comment on numbers of dead or their nationalities. He said the attack would not push the United Nations out of Afghanistan.