The Daily Telegraph reported a mob gathered around five bloody bodies. People yelled "Spy! Spy!" as a sixth corpse tied to a motorcycle was dragged through the streets, the British newspaper said.
Izzedine al-Qassam, Hamas' military wing, said in a handwritten note posted on a power pole that the six were killed for providing Israel information about fighters and rocket-launching sites.
Witnesses said four masked men pushed the victims out of a van, ordered them to lie face down in the street and shot them.
Ma'an News Agency reported Hamas Aqsa radio quoted security sources as saying the six who were killed had "possessed high-tech equipment and filming equipment to take footage of positions."
The Telegraph said two other suspected informers were killed in public earlier in the fighting between Palestinians and Israelis.