Israeli tanks hit two Hamas positions in the Gaza Strip today after activists set fire to the base of the security fence on the volatile frontier, the army said. The army said the two suspected arsonists had not crossed the fence and infiltrated Israel but it retaliated with tank fire against two Hamas observation posts. "The (army) views with great severity any attempt to damage the security fence, as well as security infrastructure," it said. The incident comes a day after Israeli soldiers detained three Palestinians who had slipped across the border from Gaza in possession of knives and grenades. The army said the trio were apprehended near an army base some 20 kilometres (12 miles) inside Israel, while police distributed pictures of hand grenades, knives and wire cutters found on them. There had already been an uptick in incidents along the border as Palestinian anger runs high over US President Donald Trump's decision in December to recognise Jerusalem as Israel's capital. On Saturday, a number of Palestinians breached the frontier and tried to torch heavy equipment. In response, Israeli jets attacked positions of Hamas, the Islamist group that controls Gaza. A day later gunfire from Gaza set off Israel's Iron Dome air defence system and in response, a tank fired at a Hamas position. The incidents come as Israel braces for the annual Palestinian Land Day protests, commemorating the killing of six unarmed Arab demonstrators in Israel in 1976, set to begin in Gaza on Friday. Gazans are being called to march towards the border fence en masse.