Algeria's top Islamic rebel group has killed four soldiers in an ambush on a military convoy and rejected any truce with the secular government, security sources said on Monday. The attack by guerrillas of the Salafist Group for Preaching and Combat (GSPC) took place on Saturday in the Batna region, 500 km (310 miles) east of the capital Algiers.The government is preparing a national referendum to give hundreds of rebels still fighting a chance to surrender in exchange of laying down their arms. A communique dated Feb. 20 published on its Web site in which it claimed responsibility for the Batna attack, said: "Our ambush against a military convoy was a great success ... we reject any truce, reconciliation or dialogue with the regime."