The Hamas Islamist group that runs the Gaza Strip says it has apprehended the killer of one of its senior commanders and that he carried out the assassination on Israel's orders.
Mazen Fuqaha, 38, was shot in the head and the chest in his car on March 24 near his Gaza home.
Israeli Defence Minister Avigdor Lieberman, in an interview with Israel's Yedioth Ahronoth newspaper soon after the killing, attributed the death to an internal power dispute in Hamas.
"We announce to the Palestinian people that the one who carried out this crime upon orders of Israeli security officers is now in the hands of [Palestinian] security services," said Ismail Haniyeh, Hamas's newly elected supreme leader, as Fuqaha's wife stood next to him, smiling.
"The direct killer who executed the crime was arrested," Mr Haniyeh told reporters, without identifying him, but saying that he had confessed to the shooting.
Israel's Shin Bet security service, which carries out covert operations against Palestinian militants, did not respond immediately to a request for a comment on Mr Haniyeh's allegations.
Israel jailed Fuqaha in 2003 for planning attacks against Israelis and sentenced him to nine life terms. He was released in 2011, as part of a group of more than 1000 Palestinian prisoners whom Israel freed in exchange for a captive soldier.
Israeli media said that after Fuqaha's release and exile to Gaza that he continued to plan attacks by Palestinian militants in the occupied West Bank.
"The occupier bears responsibility for [Fuqaha's death] because the confession [of the killer] is clear; the master who gave the orders was the occupier, the Zionist enemy," said Mr Haniyeh, but he stopped short of threatening retaliation.
In March, Hamas, which has largely observed an Egyptian-brokered ceasefire with Israel since a seven-week war in 2014, vowed Israel would pay the price for Fuqaha's killing.
Cross-border violence between Gaza militants and Israel has largely died down since that conflict.