Hamas forces killed an Islamic State supporter, the first fatality since the former launched a crackdown on the more-radical group months ago. Earlier Tuesday, ISIS supporters in the Gaza Strip gave the ruling Islamist movement Hamas a 48-hour deadline to halt its crackdown on them.
Younis al-Honnor, 27, described as a locally known Salafist leader and possibly affiliated with ISIS, was killed in a shootout with Hamas security forces when they came to arrest him at his home in Sheikh Radwan in the northern part of Gaza City, where he had illegally stockpiled munitions.
The Gaza Interior Ministry said Honnor was a criminal who had booby-trapped his house and that "explosive belts, explosive devices and rifle-propelled grenades were found inside".
A statement posted on a pro-Salafist website disputed the ministry's account. "The Hamas leadership bears responsibility for this deplorable crime," the statement said.
Witnesses said Honnor, an activist with a Salafist group, was buried in the black flag with religious inscriptions that is the standard of Islamic State insurgents who have swept other parts of the Middle East.
Palestinian President Mahmoud Abbas' cabinet in Ramallah deplored what it called Honnor's "execution".
"Hamas must respect the law and civil rights," said the cabinet statement, published by the official Palestinian news agency Wafa. "It must not mess with the souls of people. It must cease abolishing security and order and stop trespassing on the authorities of the government and the judiciary."
The Gaza-based Palestinian Centre for Human Rights questioned whether Hamas forces were justified in killing Honnor and urged a public investigation.
That call was echoed by the Palestinian cabinet, which said its attorney general would launch an probe. How that might effected remained unclear, given continues disputes between Hamas and Abbas over jurisdictions.
A statement sent to media Monday did not say what ISIS supporters would do if the crackdown continued.
The warning included a claim of responsibility for a rocket fired at Israel from Gaza last week. The claim could not be independently verified. The rocket, which was launched last Tuesday evening, landed near Gan Yavne in southern Israel, the IDF said.
A Hamas source told Ynet a day later that the group had arrested those behind the rocket strike.
"What happened yesterday (the rocket fire) goes against the interests of the Palestinian factions in the Gaza Strip and against our national interests," the source said. "We consider the rocket fire to be a dangerous thing."
Hamas has launched a crackdown on radical Islamists following a series of unclaimed bombings.
The Islamist group, which has ruled Gaza since 2007, says it views more radical groups as a threat. The extremists accuse Hamas of being soft on Israel and failing to impose religious law.
It's unclear how many IS supporters are in Gaza, or if any have operational links to the extremist group.
Meanwhile, representatives from 24 members of the international coalition against Islamic State were to meet in Paris on Tuesday. The "central" focus of the summit would be IS activity in Iraq, French Foreign Minister Laurent Fabius said last month, but added that it was “not impossible” that the talks would include Syria.
The talks will go ahead without US Secretary of State John Kerry, who made an unexpected departure from Europe at the weekend after breaking his leg in a bicycle crash in France.
The Associated Press, AFP and Reuters contributed to this report.