At least five Palestinians have been killed in an Israeli raid on a refugee camp in the West Bank town of Jenin. Witnesses said about 10 Israeli tanks - backed by armoured vehicles and jeeps and two combat helicopters - surrounded a house used by Islamic Jihad militants during the raid. Israeli military sources said an operation was in progress in the camp and that there were heavy exchanges of fire. The military says six Palestinians have been killed in the raid, while the Palestinian Red Crescent puts the toll at five.