Afghanistan said on Wednesday it had arrested or sacked hundreds of Afghan soldiers in a bid to stem a rise in insider attacks on NATO forces, a trend that threatens to undermine Western plans for a troop withdrawal.

The surge of assaults, unprecedented in modern warfare, have seen Afghan troops opening fire on their NATO colleagues more than 30 times this year, killing at least 45 foreign troops - most of them Americans.

The shootings have raised questions about the rapid growth of the Afghan army and police and alarmed alliance commanders, who have been under pressure to expand the Afghan forces to pave the way for an eventual exit of Western troops.