A Hamas security official says security forces are rounding up suspected collaborators with Israel. He says so far five people have been arrested in overnight raids.
He says suspects will go to trial and that no mercy will be shown to those who spy on other Palestinians.
He spoke on Wednesday about the condition of anonymity because he was not authorized to discuss the arrests.
In April, the Hamas government executed two accused collaborators. It was the first time the death penalty had been carried out in Gaza since the Islamic militant Hamas violently seized power there in June 2007.
Israel's Shin Bet domestic security service maintains a network of informers in the West Bank, Gaza Strip and east Jerusalem.