GAZA, Palestinian Territory 芒鈧珺次元官网网址� The Islamic militant Hamas group ruling the Gaza Strip on Thursday morning executed three Palestinians it had accused of 'collaborating' with Israel, a development that was likely spurred by the killing of a senior Hamas commander last month.

Hamas said the men were hanged at a police compound as dozens of Hamas leaders and officials watched the killing.

The three were sentenced months ago for relaying information on attack tunnels and other military details to Israel and were not directly connected to the killing of the senior commander but his death prompted their execution now.

Hamas imposed a lockdown in the wake of the mysterious killing of the militant, Mazen Faqha, 38, who was dead found with four gunshots wounds at the entrance of his Gaza City home.

The group immediately blamed Israel and Gaza "collaborators" for his death but has provided no evidence. Soon after Faqha's killing, it launched a local media campaign against those it suspects of spying for Israel.

Israel had sentenced Faqha to nine terms of life imprisonment for directing deadly suicide bombing attacks. He was freed along with more than 1,000 other Palestinian prisoners in exchange for a single Israeli soldier in 2011.

Hamas has executed 25 people sentenced under its judicial system since 2007 when it took over Gaza in bloody street battles from forces loyal to Palestinian President Mahmoud Abbas.

Rights groups have questioned the fairness of trials under the Hamas system.

"The death penalty is a barbaric practice that has no place in a modern state," Sarah Leah Whitson, executive director of the Middle East division of Human Rights Watch, said.

"The abhorrent executions by Hamas authorities of three men in Gaza deemed to be collaborators project weakness, not strength," she said. "Hamas authorities will never achieve true security or stability through firing squads or by the gallows, but rather through respect for international norms and the rule of law."

Hamas also killed 23 people without trials during its 2014 war with Israel.

After Faqha's killing, Hamas set up checkpoints throughout Gaza and barred all residents and foreign aid workers from leaving the coastal strip and going to Israel.

It has since eased some of the restrictions and allowed some Palestinians, mostly those needing medical treatment, relatives of prisoners in Israel and some international aid workers, to cross into Israel.

Fares Akram, The Associated Press