Four people were shot dead by Afghan security forces on Saturday as protests over the burnings of the Muslim holy book at a NATO base erupted for a fifth day.

Protesters were attempting to bombard a U.N. compound in the north.

The burning of the Korans at the Bagram compound this week has deepened public mistrust of NATO forces struggling to stabilise Afghanistan before foreign combat troops withdraw by end-2014.

Friday was the deadliest day of prostests, with 12 dead.