Viet War Action Opens after Truce(c) N, Y, Times News Service SAIGON — The Allied forces said today that the Viet Cong and the North Vietnamese had violated the 24-hour cease-fire marking the birthday of Buddha with 22 significant incidents,” These were said to have resulted in the death of 15 men and the wounding of 19. Seven enemy troops were killed and two captured. The truce ended at midnight on Tuesday,An American military spokesman announced the loss on Monday—before the truce began— of three Air Force Phantom jets, a light observation plane and two Marine Corps helicopters, The shooting down on Monday of a Navy Phantom and a Navy helicopter was announced yesterday.The most serious of the truce violations occurred in Qung-ngai province in the north. Six members qf the lQlst Airborne Division were killed and nine wounded when their patrol was ambushed by an estimated enemy company.Helicopter gunships and Ac*47 Dragonships were called in to blast the attackers, and they broke contact within 45 minutes. Two members erf the 1st Cavalry Division (Airmobile), occupying what were termed defensive positions near Duchpho, were killed by snipers. In the ensuing Crefight four enemy troops were slain. An 82-mm mortar and ammunition were captured.