KABUL - Insurgents clad in burkas attacked a coalition base in Kabul with guns and rocket-propelled grenades on Saturday, but were killed either when they detonated their explosives or by Afghan or coalition fire outside the entrance, NATO and police said.Three "friendly forces" -- NATO or Afghan troops -- were lightly wounded in the assault on Camp Phoenix, a large base near the capital's airport, but no civilians or soldiers were killed.The assault was launched a day after protesters enraged by the burning of a Koran by an obscure US pastor over-ran a UN compound and killed at least seven international staff in the worst-ever attack on the United Nations in Afghanistan.