Rabat – In the “most serious” escalation of the conflict between Israel and Hamas since the summer of 2014, the Israeli military (IDF) said it had carried out air strikes on four targets in the occupied Gaza Strip on Thursday, as a response to mortar rounds fired into Israel. One of the strikes – which the Israeli army said targeted “terrorist infrastructure sites” – targeted a metal workshop and led to the injury of three children and a 65-year-old, the Gaza Health Ministry said, according to a report by Al Jazeera.No organization, including Hamas, has claimed responsibility for the trigger mortar rounds, but Israel holds Hamas responsible for attacks coming out of the territory. The IDF confirmed that the targeted sites belonged to Hamas, the group that governs Gaza, and Palestinian media outlets said the strikes also hit an outpost of a terrorist group called Islamic Jihad.On Wednesday, Israel struck five additional Hamas targets after claiming that a mortar shell had been fired against its forces near Gaza. The IDF said the attack did not injure or kill any soldiers or civilians, according to the Washington Post.In summer 2014, the Israeli army killed more than 2,000 people, mostly Palestinians, in the Gaza strip through airstrikes as part of its war against Hamas and other groups in the territories the Jewish state occupies.Israeli forces found and destroyed a tunnel linking Gaza and Israel last month – the first one discovered since the strikes two years ago. The development spurred concerns that Hamas had begun rebuilding its tunnel network in preparation for a series of new suicide attacks.