The young man asked us not to identify him. He had "made a mistake", he said, when someone apparently overheard him criticising a Hamas leader in a street conversation with friends. "We call them 'drones' - people Hamas pays to listen for them." This was during Israel's recent three-week military offensive in Gaza. That evening more than a dozen armed men with black facemasks came to his home and took him to an isolated area, where they shot him three times in his legs and ankles.

His was one of the scores of cases that Human Rights Watch and Palestinian human rights groups have documented of masked gunmen apparently affiliated with Hamas abducting Palestinians and maiming them by shooting them in the legs. Others were badly beaten with iron rods and gun butts, leaving many with broken arms and legs. They at least lived to tell about what happened: alleged Hamas gunmen executed at least 18 men, most of them suspected of collaborating with Israel, who had fled Gaza's central prison after Israel bombed it on 28 December. Another 14 men have been killed since mid-January, when heavy fighting with Israel ended, including eight who, according to Palestinian human rights groups, were beaten or tortured to death, at least six of them in the custody of Hamas security forces.

Many of the victims were affiliated with Fatah, Hamas's main political rival, especially those who had once worked for Fatah-led security forces. This intra-Palestinian political violence - in the Fatah-run West Bank as well as Gaza - is not new. Hamas's internal takeover in Gaza in June 2007 was perhaps the bloodiest of these episodes. But the killings, beatings, and torture in Gaza in 2009 come at a time when Hamas exercises effective political control of the Gaza Strip.

Last week in Gaza City, Human Rights Watch met officials from Hamas and the interior ministry they control, to discuss our findings. They told us they had completed investigations into two of the 32 documented killings, and investigations in another two cases were ongoing. But four investigations in the aftermath of 32 killings, and scores of other serious abuses by Hamas security forces or affiliated militia hardly begin to address the problem. They also said that Hamas could not have prevented killings and shootings that occurred during Israel's offensive, but the systematic nature of the executions and maimings, and the fact that they have continued since the end of heavy fighting, undercuts these claims.

On 20 April, a few hours after we released our report, Hamas called a news conference in Gaza City. Fawzi Barhoum, a Hamas spokesman and one of those with whom we had met a few days earlier, said our report was "hasty" and "incomplete", although he did not note any errors, and blamed the attacks on "the Israeli occupation, which deliberately destroyed the security system in the Gaza Strip". He also said that our report blamed the killings on Hamas "without any evidence".

We found the allegations of victims and witnesses that the perpetrators of these attacks were Hamas-affiliated to be consistent and credible. Israel's military did attack Hamas security forces, including some apparently unlawful attacks on civilian police and civilian structures. But despite Israel's continuing refusal to allow us access to Gaza, Human Rights Watch researchers were able to enter via the Egyptian-controlled Rafah crossing a few days after the Israeli offensive ended. It was clear then, and has been since, that Hamas's security forces were well organised and had the capacity to maintain internal order. It was extremely unlikely then, and even less likely now, that other armed groups or criminal gangs would be able to move about freely and carry out these attacks. And, although reports of incidents have declined, violent attacks have continued through April.

  • Human Rights Watch has also documented a range of serious violations of international humanitarian law by Israel in connection with its military offensive in Gaza and the continuing blockade of the territory.