Israel’s military stormed a mosque in the occupied West Bank on Thursday, where it said weapons were being stored, and engaged in gun battles that left at least five Palestinians dead, including a young militant commander who Israel says was responsible for attacks against Israeli civilians.

It was the second straight day of an Israeli incursion into the northern West Bank, focused in and around the cities of Tulkarm and Jenin, involving columns of armored vehicles, fleets of drones and hundreds of troops. The raids are Israel’s biggest military actions in the West Bank in more than a year.

The commander killed in Thursday’s fighting, Muhammad Jaber, who died in a clash in Tulkarm, led the local branch of the militant group Palestinian Islamic Jihad, which confirmed his death. Palestinian Islamic Jihad, like its ally, Hamas, receives financial support, weapons and training from Iran, according to the U.S. State Department.

The raid in the West Bank is an escalation along a third front for Israel, in addition to the war with Hamas in the Gaza Strip, and the increased air attacks across its northern border with Lebanon against the militant group Hezbollah, which is also backed by Iran.

Wafa, the Palestinian Authority’s official news agency, said 17 people had been killed in total in the raids across the West Bank that began before dawn on Wednesday, without specifying whether militants were among them. The Israel military said that 16 militants had been killed across the West Bank.