A Gaza security official says Hamas has killed 11 suspected informers for Israel.
Friday's killings came a day after Israel killed three top Hamas military commanders in an airstrike on a house in southern Gaza Strip.
Hamas has vowed revenge for the targeting of its leaders.
The security official says the 11 suspected informers were killed early Friday at the Gaza City police headquarters. He says the 11 men had previously been sentenced by Gaza courts.
He spoke on condition of anonymity because he was not authorized to discuss incident with reporters. The killings of the 11 were also reported by Al Rai and Al Majd, two websites linked to Hamas.
Israel's intelligence services rely, in part, on informers to pinpoint the whereabouts of Hamas leaders.