Hamas authorities in Gaza have begun imposing the death penalty as part of a campaign against Palestinians found guilty of collaborating with Israel.

Two men have been executed in Gaza this year for passing information to Israeli forces. Dozens more are in jail.

But human rights workers say the executions have been carried out in violation of Palestinian law.

Omar Kaware is one of 42 men who share a single prison cell in Gaza's main jail.

Metal bunks cram the room and the inmates share one toilet and one bathroom between them.

Every one of these men is accused of spying for Israel. And several, including Mr Kaware, have been sentenced to death.

"They accused me of collaborating with the Israelis, but I'm innocent," he said.

Mr Kaware was accused of giving information to Israeli forces which helped them pinpoint and assassinate a string of Palestinian militants.

He says he was set up by a vengeful neighbour and was tortured into making a confession.

He revealed scars on his hands and feet as evidence.

"They beat me. They tied my arms to the ceiling, hit me all over," he said.

Prison officers here say collaborators or informants are among the most despised people in Palestinian society.

Although they acknowledge many become collaborators only because they are blackmailed or coerced.

Nevertheless, the director of Gaza's prison system, Nasir Suleiman, says he supports execution in the worst cases.

"One collaborator gave information about a top resistance leader," he said.

"The Israelis then fired a missile, killing him and many other Palestinians."

Last April, two collaborators were executed in Gaza - the first time in five years that authorities in Gaza or the West Bank have carried out a death sentence handed down by a Palestinian court.

And human rights workers, including Mahmoud Abu Rahma, predict more will follow.

"There are indicators that authorities in Gaza do intend to increase the executions, the death penalties," he said.

In fact the death sentence is not uncommon in Gaza or the West Bank.

But Palestinian law dictates the president, now Mahmoud Abbas, must sign off before a sentence is carried out - something he has been reluctant to do.

But Mahmoud Abu Rahma says Hamas rulers in Gaza who refuse to recognise the president's authority are now illegally approving the executions themselves.

"Now the basic law states that the prime minister assists the president in implementing the law," he said.

"They interpreted this as the prime minister, for them in Gaza, Mr Ismail Haniyeh, can actually assist the president in implementing the court rulings, which includes the death penalty."

Gaza's jail is already overcrowded and the collaborators' cell at least looks set to become even more so.