Palestinian gunmen ride motorcycles as they drag the body of a man, who was suspected of working for Israel, in Gaza City, Tuesday. GAZA - Six Palestinians suspected of giving information to Israel during its airstrike campaign have been killed in the Gaza Strip. One of them was dragged after his death through the streets behind a convoy of motorcycles, as some people appeared to celebrate in scenes that a leading Hamas figure described as "completely unacceptable." Citing an unidentified security source, Hamas' al-Aqsa radio station said the six men were shot dead on Tuesday after being "caught red-handed" working for Israel. "They possessed hi-tech equipment and filming equipment to take footage of positions," al-Aqsa radio station said. However, on Wednesday Hamas' deputy leader Moussa Abu Marzouk condemned what he called the "unlawful" killings, Reuters reported. In comments posted on his Facebook page on Wednesday, Abu Marzouk urged the Islamist Hamas administration ruling Gaza to ensure that no one takes the law into their own hands. "Punishing collaborators and especially those involved in the killing of our leaders must only be carried out in accordance with the law and through the legal procedures," he said. "The way those collaborators were killed and the images after their death were completely unacceptable," he added. "Those who did it should be punished and it must not be repeated," said the Hamas official, who is currently in Cairo. Photographs showed one of the bodies, partially clothed, being dragged through the streets of Gaza behind a motorcycle as others rode in convoy alongside. At least one body was beaten, kicked and trampled, Reuters reported. Israeli security officials acknowledge they rely on a network of Palestinian informants to identify targets, The Associated Press said. The New York Times reported that another man, named as Ashraf Ouaida, was killed by masked gunmen Friday because he was suspected of collaborating with Israel. He was shot several times and his body was left with a sign round his neck accusing him of helping Israel kill 15 Palestinian leaders and beneath a billboard featuring a Hamas fighter holding a rocket, the newspaper said.