By Nidal al-Mughrabi

GAZA, May 31 (Reuters) - Human Rights Watch has urged the Hamas government in the Gaza Strip to investigate the abduction and alleged torture of three Palestinians by an Islamist militant group that accused them of spying for Israel.

The three were seized on May 20 by Islamic Jihad, which said they had helped Israeli forces kill several militants, including one of its leaders. After making taped confessions, the men were handed over to the Hamas-run Interior Ministry for prosecution.

A ministry spokesman, Ehab al-Ghsain, said the detainees bore signs of torture. Islamic Jihad denied having abused them.

The New York-based rights group issued a statement on Friday calling on Hamas, which took over Gaza a year ago after routing the forces of Western-backed Palestinian President Mahmoud Abbas, to exercise sole responsibility for law enforcement.

"An armed group like (Islamic Jihad's) al-Quds Brigades has no legal right to arrest, detain or interrogate suspects," said Joe Stork, deputy director of Human Rights Watch's Middle East and North Africa division.

"The Hamas authorities in Gaza, who control the governing institutions there, have a duty to prosecute those responsible for these abductions and apparent use of torture," Stork said.

Hamas should charge the three suspected spies "with a recognisable criminal offence and try them in accordance with international standards" or free them, Human Rights Watch added.

Ghsain said Hamas had rebuked Islamic Jihad over the abductions, but no legal action against the group was planned.

"There were marks of torture (on the suspects) and we expressed our displeasure to Islamic Jihad and told them what happened must not be repeated," he said.

"We have warned all parties against carrying out such act in isolation from the official agencies."

Islamic Jihad, which like Hamas has spearheaded an almost eight-year-old uprising against the Jewish state but lacks Hamas's political profile, defended its actions.

"While we fight the Israeli occupation we must fight collaborators who endanger the lives of leaders and society in general," said Daoud Shehab, the group's spokesman.

"We have acted legally and fairly," he said. "The three collaborators were not tortured by any means and they gave full confessions of their own free will."

Several suspected spies for Israel have received death sentences in Palestinian courts and dozens of others have been executed by armed militants in Gaza and the Israeli-occupied West Bank. The phenomenon has been condemned internationally.

Ghsain said the three detainees were being interrogated by Hamas authorities and could be prosecuted if convicted. Dozens of suspected spies are in Gazan prisons awaiting trial, he said. (Editing by Elizabeth Piper)

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