A memorial service was held in Jerusalem on Sunday for four UN peacekeepers killed last week during Israel's offensive in Lebanon, and UN Secretary General Kofi Annan said that many questions that still surround their deaths must be answered. About 70 people, including UN officials and relatives of one of the four slain peacekeepers, attended the service in the garden courtyard of the UN Truce Supervision Organization. The four peacekeepers were Du Zhaoyu of China, whose wife was in attendance; Paeta Hess-Von Kruedener of Canada; Hans-Peter Lang of Austria; and Jarno Makinen of Finland. They were believed to have died in direct shelling by Israeli forces on their position in southern Lebanon. UN observers had telephoned the Israeli military 10 times in six hours to ask it to stop shelling near their position before the attack on Tuesday, which sparked international anger with Israel. The UN observation post near Khiam came under close Israeli fire 21 times that day - including 12 hits within 100 yards and five direct hits from 1:20 p.m. until the peacekeepers' post was destroyed at 7:30 p.m., Jane Lute, assistant secretary-general for peacekeeping, told the UN Security Council in New York. UN officials said Hizbullah gunmen had been operating in the area of the post near the eastern end of the border with Israel, a routine tactic to prevent Israel from attacking them. But in a letter read at Sunday's memorial service, Annan said: "Many questions surround the tragic deaths of these unarmed peacekeepers, and these must be answered." Annan had earlier said the Israeli attack was "apparently deliberate." His letter, read at the service by Alvaro de Soto, the UN's special coordinator for the Middle East peace process, also said the UN feared another member of its civilian staff was killed in the heavily bombarded Lebanese city of Tyre. Large photographs of the four killed peacekeepers were displayed on four separate tables with national flags and medals they had earned for their service. The Chinese and Finnish men were smiling in the photos, the Canadian looked to be on the verge of cracking a smile, and the Austrian stared earnestly at the camera. Soldiers from each of the four countries paid tribute in short speeches to each of the victims. De Soto said at the service that the ongoing carnage "horrific." "The conflict must come to an end without further delay," he said. UN flags flew at half mast and 32 peacekeepers in military uniforms and their signature blue berets stood at attention. "The men who died on Tuesday at Control Base Khiam were the eyes of the world," Annan's letter said. "May these brave men rest in peace."