The Palestinian Islamist group Hamas launched an unprecedented attack on Israel on Saturday, firing thousands of rockets from the Gaza Strip into Israel, as dozens of fighters infiltrated the heavily fortified border in several locations by air, land and sea. The offensive caught the country completely off guard and represents a “historic failure” for Israeli intelligence services, according to Middle East expert David Khalfa.

Several hours after the incursion began, Hamas militants were still fighting gunbattles inside several Israeli communities near Gaza. Israel’s national rescue service said at least 40 people have been killed and hundreds wounded, making it the deadliest attack in the country in years.

The escalation comes against a backdrop of surging violence between Israel and Palestinian militants in the West Bank, which together with the Gaza Strip is part of the territories where Palestinians have long sought to establish a state.

It also comes at a time of political upheaval in Israel, which has been riven by deep divisions over moves to overhaul the judiciary in recent months.

David Khalfa, co-director of the North Africa and Middle East Observatory at French think tank the Fondation Jean-Jaurès, says Hamas is taking advantage of Israel’s vulnerability to carry out its deadly “Operation Al-Aqsa Storm”.