The leader of an anti-Hamas group that was armed and backed by Israel has been killed in Gaza, the group confirmed Thursday, in a potential blow to Israel’s post-war plans in the shattered territory.

Yasser Abu Shabab, who led a militia controlling a patch of territory in Rafah in southern Gaza, was killed while trying to “de-escalate a conflict” between members of a family in a public square, the organization said. One Israeli source said earlier the death resulted from “internal clashes.”

Two Israeli sources said that Israel tried to evacuate Abu Shabab to a hospital in the country’s south before he was pronounced dead.

Abu Shabab was the leader of the most prominent of several Israeli-backed armed groups in Gaza, and his death could prove to be a setback to Israel’s still-unclear plans for the future of the enclave. Abu Shabab, who was in his early 30s, appeared to be spreading his reach slowly in southern Gaza as he tried to carve out an area free of Hamas. Israel intended to use Abu Shabab’s militia to weaken Hamas, as an alternative to the militant group’s Islamist rule.

Israel also planned to use Abu Shabab’s organization, which he called the “Popular Forces,” to secure reconstruction projects inside Israeli-occupied Gaza under the next phase of the ceasefire deal. During the last several months of the war, Abu Shabab helped control the flow of aid from the Kerem Shalom crossing in southern Gaza.

Hamas, which had previously vowed to target Abu Shabab, called him a traitor but did not explicitly claim responsibility for his death. The militant group said he faced “the inevitable fate of anyone who betrays their people and homeland, agreeing to be a pawn for the Occupation.”

In a statement, Hamas commended all those who denounced Abu Shabab and others “collaborating” with Israel.

“We emphasize that the Occupation, just as it failed to protect its agents, cannot protect any of its collaborators,” Hamas added.

The Popular Forces stressed that Abu Shabab was not killed by Hamas.

“We strongly deny any and all misleading reports suggesting that he was assassinated by thugs from the terroristic gang Hamas, as it is way too weak to take out the General Leader,” the group said in a statement.

Pictures circulated on multiple Gaza messaging groups showed a number of Palestinians celebrating Abu Shabab’s death. One picture obtained by CNN shows Abu Shabab with a red “X” over his face and calls him a “pig.”

Abu Shabab was the leader of one of several loosely organized Palestinian gangs that Israel backs in Gaza, and its members largely stay within the Israeli-occupied part of the enclave.

Abu Shabab’s group, which he claimed numbered in the hundreds, would carry out raids in Hamas-controlled territory before retreating quickly back to Israel’s protection, according to Muhammad Shehada, a Gaza expert with the European Council on Foreign Relations.

In the absence of a post-war governance plan for Gaza, Israel has backed these armed groups, which have staked out small bits of territory in different parts of the strip. Prime Minister Benjamin Netanyahu called the gangs “a good thing,” even as his political rivals attacked him for arming “the equivalent of ISIS in Gaza.”

The ongoing operation to arm the groups, including that of Abu Shabab, was authorized without security cabinet approval, two Israeli officials told CNN in June. (CNN)

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