Clashes between guerrillas and South African-led security forces in Namibia continued as U.N. peacekeepers prepared to help the rebels withdraw to Angola. A police spokesman said three gun battles were fought as government forces. No casualties were reported. Meanwhile, the U.N. Transition Assistance Group began setting up assembly points in the barren bush country of northern Namibia, the first step in an agreement worked out over the weekend that calls for rebels of the South-West Africa People’s Organization to return to their bases in Angola.