“As the security forces exited the city, a military vehicle was hit by an explosive device, damaging the vehicle,” the army said, adding that helicopters “opened fire toward the gunmen in order to assist in extraction of the forces.”Israeli military spokesman Lt. Col. Richard Hecht said that hours after the initial firefight, the army had flooded the area with troops in order to extract personnel pinned down in five disabled vehicles at the scene, describing it as an “evacuation” operation.

“We’re bringing in heavy equipment to get these vehicles out,” Hecht told reporters.

The militants’ use of a roadside bomb in the West Bank was “very unusual and dramatic,” Hecht said, adding that it may affect future military strategy in the territory.

Unconfirmed amateur video footage from Jenin appeared to show a roadside explosive targeting an Israeli armored vehicle. Another video posted online appeared to show Israeli military helicopter launching a rocket during the ongoing army operation.

The Israeli military rarely uses aircraft in its operations in the occupied West Bank. Israeli media reported that it was the first use of an attack helicopter in the territory since the Palestinian uprising in the early 2000s.

The Palestinian Health Ministry identified those killed as Khaled Asasa, 21, Qassam Abu Sariya, 29, Qais Jabarin, 21, and 15-year-old Ahmed Saqr, and said at least five others remained in serious condition after being wounded in the shootout.

Hussein al-Shekh, a senior Palestinian official, accused Israel of waging “a fierce and open war” against the Palestinian people and said President Mahmoud Abbas would make “unprecedented decisions” in an upcoming emergency meeting.

Egypt’s Foreign Ministry condemned what it called Israel’s “continued escalation against the Palestinians,” saying it only further inflamed the situation and undermined efforts to reduce regional tensions.

Israel and the Palestinians have been gripped by months of violence, focused mainly in the West Bank, where some 124 Palestinians have been killed this year. The city of Jenin has been a hotbed of Palestinian militancy.

Israel captured the West Bank in the 1967 Mideast war, along with east Jerusalem and the Gaza Strip. The Palestinians seek those territories for a future independent state.

Israel has been staging near-nightly raids in the West Bank in response to a spasm of Palestinian violence early last year. Palestinian attacks against Israelis have surged during that time.

Israel says most of the dead were militants, but stone-throwing youths protesting the incursions and others not involved in confrontations have also been killed.

Palestinian attacks against Israelis have killed at least 20 people this year.