Gaza gunmen killed 18 alleged spies for Israel on Friday, including seven who were lined up behind a mosque and shot after midday prayers, in response to Israel's deadly airstrikes against top Hamas military commanders.
Hamas media portrayed the killings as the beginning of a new crackdown, under the rallying cry of "choking the necks of the collaborators." It was the largest number of suspected informers killed by Hamas in a single day since it seized Gaza by force in 2007.
The Al Majd website, which is close to the Hamas security services, said suspects would now be dealt with "in the field" rather than in the courts in order to create deterrence.
Hamas said it would not release the names of those killed because it wanted to protect the reputation of their families. The Palestinian Center for Human Rights said two of those killed Friday were women. It called for an immediate halt to what it said were "extra-judicial executions."
The killings came a day after an Israeli airstrike on a house in southern Gaza killed three senior military leaders of Hamas. The three had played a key role in expanding Hamas' military capabilities, including building a network of attack tunnels into Israel and smuggling weapons.
Earlier in the week, another strike killed the wife and two children of Mohammed Deif, the shadowy leader of the Hamas military wing. Deif's fate remains unclear.
Friday's events began with the shooting of 11 alleged informants at the Gaza City police headquarters in the morning. Of the 11, two were women, the Palestinian rights centre said.
Later in the day, seven people were killed outside the city's downtown al-Omari mosque as worshippers wrapped up noon prayers. Several dozen people were outside the mosque at the time, said one of the witnesses, 42-year-old Ayman Sharif.
Another witness said the faces of the seven had been covered. He spoke on condition of anonymity because he was afraid for his own safety.
Sharif said masked gunmen lined up seven people against a wall. A piece of paper was affixed above the head of each of them, with his initials and his alleged crime.
Sharif quoted one of the gunmen as saying the seven "had sold their souls to the enemy for a cheap price" and had caused killing and destruction.