Israeli attack helicopters have struck Hamas military positions in Gaza, after the army said a balloon-borne “explosive device” from the Palestinian enclave targeted its territory. Monday’s raid, which resulted in damage to the Hamas positions but no casualties, was the third tit-for-tat exchange in as many days. Three military observation posts were hit in the south and center of the Hamas-ruled coastal strip, according to a Palestinian official. The Israeli military earlier said its air force struck “two Hamas military posts” in response to the latest launch of a balloon-borne device from Gaza. “A cluster of balloons carrying an explosive device was launched from the southern Gaza Strip towards Israeli territory,” the army said. “No injuries or damage were reported.” Palestinians in Gaza have for months flown clusters of balloons with incendiaries or explosives suspended beneath them across the border into Israel as weekly protests and clashes have continued along the frontier, AFP reports.