Hamas security forces are routinely subjecting Palestinian detainees in Gaza to torture and abuse, according to a report by Human Rights Watch, which says three men have been executed on the basis of "confessions" apparently obtained under coercion.

The report cites serious abuses such as arbitrary arrest, denial of access to lawyers and the use of torture during interrogations.

"After five years of Hamas rule in Gaza, its criminal justice system reeks of injustice, routinely violates detainees' rights, and grants immunity to abusive security services," said Joe Stork of HRW. "Hamas should stop the kinds of abuses that Egyptians, Syrians and others in the region have risked their lives to bring to an end."

The report, Abusive System: Criminal Justice in Gaza, calls for urgent reforms, including a moratorium on the death penalty. It cites the case of Abdel Karim Shrair, who, according to family and lawyers, was tortured under interrogation before being executed by firing squad in May 2011 after "confessing" to collaborating with Israel.

Fourteen Palestinians have been executed since Hamas took control of the Gaza Strip in June 2007. This week, the European Union condemned death sentences handed down last month to two men in Gaza, one for murder and the second for collaboration.

The EU "considers capital punishment to be cruel and inhuman, failing to provide deterrence to criminal behaviour, and representing an unacceptable denial of human dignity and integrity", it said in a statement.

HRWatch accused Hamas of failing to investigate alleged cases of torture and abuse, and of granting impunity from prosecution to security service officials.

It said "intra-Palestinian political rivalry [between Hamas and Fatah] remains a significant factor behind many Hamas abuses against detainees in Gaza".

The Fatah-dominated Palestinian Authority in the West Bank also "arrests and detains Palestinians arbitrarily, including Hamas members or sympathisers, and similarly subjects detainees to torture and abuse", the report said.