A top commander of a small militant Palestinian group was killed on Friday in Gaza City when his car mysteriously exploded in flames.
Witnesses said he was the target of an Israeli air strike, but the Israeli military, which has killed dozens of militant leaders, denied involvement.
The blast was part of a widening spiral of violence that illustrates the challenges the Islamic militant Hamas can expect after taking power on Wednesday. On Thursday evening, a Palestinian militant from a rival group killed four Israelis in a suicide bombing in the West Bank.
Hospital officials identified the dead man as Abu Yousef Abu Quka, a senior commander of the military wing of the Popular Resistance Committees in the Gaza Strip. The white Subaru in which he was driving was reduced to a hunk of twisted, charred metal.
Israel Radio reported that Abu Quka oversaw numerous rocket attacks on Israel. Members of his group said Israel had tried to assassinate him in the past.
The blast came just hours after a suicide bomber affiliated with Palestinian leader Mahmoud Abbas' Fatah Party dressed as an Orthodox Jew and hitched a ride in a car driving to the West Bank settlement of Kedumim. The bomber blew himself up at the entrance to the settlement, also killing the four Israelis in the car. It was the first time a suicide bomber has blown up in a private car.
The suicide attack was the first by a Fatah affiliate since a February 2005 truce. Israeli security officials say they expect more suicide bombings from Fatah militants now that the rival Hamas group has taken power.
With Israel's acting Prime Minister Ehud Olmert planning to pull out of much of the West Bank, and the long-ruling Fatah out of power, Al Aqsa militants might want to revive Fatah's credibility on the Arab street by creating the impression that Israel is retreating under fire. Hamas militants, then outside the government, did the same ahead of Israel's Gaza Strip evacuation.
Alternatively, security officials said, Al Aqsa might want to turn up the heat on Hamas, which ousted Fatah in Jan. 25 parliamentary elections, and is already facing aid cutoff threats from the West for refusing to renounce its violent campaign against Israel.
Abbas, traveling in South Africa, denounced the attack. "We as the Palestinian Authority do not accept it," he said. "We condemn it."
Hamas spokesman Sami Abu Zuhri said "it is our people's right to resist occupation. Israel is responsible for such attacks because of its daily aggression against our people."
David Baker, an official in Olmert's office, said Thursday that the attack "took place while the Palestinians refused to lift a finger to prevent terror attacks against Israelis, and we saw the results tonight," reports the AP.
An intense movement of NATO aircraft was reported at Poland's Rzeszow airfield near the Ukrainian border