A senior Hamas official on Monday suggested that Israel was behind an explosion that killed two of his group's operatives in Beirut on Saturday. "We must not rule out the possibility that the Zionist enemy is responsible for this act of cowardice," Army Radio quoted a Hamas official as saying during the funeral of the two men killed in the blast. Hamas confirmed Sunday that two of its members - Basil Juma, 29, and Hassan Hadad, 21 - were killed in the mysterious late-night expulsion, and the Palestinian terror group then said it was still trying to determine who was behind the attack. Lebanon's state-run news agency said Saturday's explosion was caused by three bombs tied to each other and placed under a car believed to belong to a Hamas official. The blast took place near Hamas offices south of Beirut. The statement did not specify the men's role in the group, but it referred to them as "fighters" - usually a reference to low-level members of the group's armed wing. Osama Hamdan, a senior Hamas representative in Lebanon, said the bomb targeted "offices used by the group with a living quarters for bodyguards." Lebanon houses about a dozen Palestinian refugee camps with some 200,000 registered refugees. Explosions in the area, a stronghold of Hizbullah, are rare. Hizbullah has its own arsenal with tens of thousands of rockets and missiles, which it says it needs to fight off any threat from Israel. Also Saturday, UN peacekeepers found "a significant quantity of explosives" in southern Lebanon, just 4 kilometers from the Israeli border. The UNIFIL peacekeeping force announced the find Sunday, but offered no further details. The explosives were found in Khiam, where a blast in 2007 killed six UN peacekeepers. Government spokesman Mark Regev accused Hizbullah of being behind the arms cache, and said the group, with backing from Iran, was violating a UN-brokered cease-fire that ended the Second Lebanon War. "Israel has expressed our concern over a period of months and even longer as to the Hizbullah rearmament. There is no doubt that the leadership in Teheran, while brutalizing its own population, is continuing to systematically arm its proxy in Lebanon."