The Soviet Union has withdrawn MiG-23 and Tu-16 planes from its base at Cam Ranh Bay in Vietnam, a Foreign Ministry spokesman said Thursday. Cam Ranh Bay, a former American base during the Vietnam War, is the Soviets' largest foreign base, according to U.S. military sources. As of 1985, a reported 30 ships were based there. A squadron with six to 10 aircraft remains at the field, said spokesman Vadim Perfiliev. He gave no other details. MiG-23s are fighters. Tu-16 Badgers are variously fitted out as bombers and electronic reconnaissance aircraft.