GAZA, Oct 3 (Nidal al-Mughrabi/Reuters) - Officials of Gaza's Islamist Hamas government turned up at a news conference by Human Rights Watch in Gaza on Wednesday to dispute an HRW report accusing Hamas of torture and other abuses of justice in the Palestinian enclave.

The surprise appearance by government representatives turned the news conference into an open debate, an uncommon display in the Gaza Strip where Hamas in the past would probably have remained aloof or prevented such a press event on its turf.

The Human Rights Watch report - researched in Gaza with the knowledge of the Palestinian Islamist movement - said Hamas subjects Palestinians to serious abuses of justice, including torture, arbitrary arrest and unfair trials.

The Islamist faction said the report was politically motivated. Hamas has run Gaza unopposed since it seized control in 2007, suppressing rivals in the Fateh movement and launching sporadic attacks against Israel, which maintains a partial blockade of the coastal strip to prevent the entry of arms.

Bill Van Esveld, an HRW Middle East researcher who chaired the press conference, said the presence of Hamas media officials was surprising. They knew it was happening but they were not invited, Esveld told Reuters.

Hamas refuses to accept the legitimacy of the state of Israel and is ostracized in the West as a perceived terrorist group. But its ties with Iran have frayed since the Arab Spring of popular uprisings and it is now allied to Egypt's elected Muslim Brotherhood rulers and working to improve its image.

Hamas cooperated with HRW's Joe Stork, deputy Middle East director of the New York-based rights group, who visited the enclave to conduct interviews and research. It did not reply to his written questions, but Stork did meet the minister of justice and the director of internal security.

They were not quoted in the 43-page report, Hamas said.

ROUTINE RIGHTS VIOLATIONS

Islam Shahwan, spokesman for the Hamas interior ministry, confronted Esveld and accused the rights group itself of failing to reflect the reality of the situation in Gaza.

Your report has many mistakes in it, Shahwan told Esveld before the television cameras.

The report is based on interviews with ex-detainees, prisoners' families, lawyers, officials and human rights activists.

Human Rights Watch, which is based in New York, urged Hamas to stop the kind of abuses that Egyptians, Syrians and others in the region have risked their lives to bring to an end - an allusion to Arab Spring uprisings.

After five years of Hamas rule in Gaza, its criminal justice system reeks of injustice, routinely violates detainees' rights and grants impunity to abusive security services, Stork said in a statement.

Human Rights Watch said witnesses reported that Hamas's Internal Security agency, the drug unit of the civil police force and police detectives have all tortured detainees.

The Hamas authorities have failed to investigate and prosecute abusive security officials, and have in practice granted immunity from prosecution to officials in the Internal Security service in particular, Human Rights Watch said.

Shahwan said the report was politically motivated and relied, in part, on guessing rather than on facts.

He acknowledged, however, that Hamas authorities had dismissed or detained 120 members of the security forces for what he termed violations since 2007.

Calling for a moratorium on the death penalty, the report said Hamas had executed three men in the past five years, convicted on confessions apparently made under torture.

Some of the Gaza abuse cases documented were against people detained on suspicion of collaborating with Israel or the Palestinian Authority in the West Bank, it said. Collaboration is a serious crime under Palestinian law, but suspicion of collaboration does not justify torture or other abuse. (Editing by Douglas Hamilton and Mark Heinrich)