Three Palestinian terrorists killed in an air strike late Wednesday night were planning to carry out an imminent large-scale terror attack in Israel, the IDF said.Two of the main operatives, Abu al-Anis and Ashraf Mahmud Salah – both aged 32 and of Rafah – belonged to a shadowy terrorist organization called the Defenders of al-Aksa, which the Shin Bet (Israel Security Agency) considers to be an offshoot of Hamas, and which is activated by Hamas when it wishes to carry out “low signature” attacks that do no lead directly back to it.The three men were killed on Wednesday when the air force struck a white van they were traveling in Gaza.In the past, two of the terrorists attempted to smuggle explosives out of Gaza into Israel via the Sinai Peninsula, and perpetrate attacks in the West Bank, the IDF said. One of the men also tried to assist two Egyptian terrorists to carry out a suicide bombing in Israel, the IDF added.The IDF said Hamas was aware of the terror plot.The Defenders of al-Aksa consists of Hamas armed wing members, as well as terrorists from other Palestinian factions in Gaza. Past members arrested in recent years have been charged with a host of terror activities, from laying roadside bombs, to sniping attacks, to firing antitank missiles at IDF forces, as well as firing shells and rockets.Defenders of al-Aksa is headed by Mamed Sabahi Tamaraz, a resident of Jabalia, according to a 2011 Shin Bet report made public on its website.The organization was founded and funded by Hamas Interior Minister Fathi Ahmed Hammad. The group receives its orders directly from Hamas, according to Israeli security forces.In 2008, the group carried out a shooting attack on a convoy carrying then-public security minister Avi Dichter near Kibbutz Meflasim, near the Gaza border. Dichter is now the home front defense minister.Meanwhile, on Thursday, an IDF unit patrolling the border with northern Gaza came under mortar fire from the Strip. Two mortar shells fired at the soldiers failed to cross the border, and landed inside Gaza. No injuries were reported.