Gaza's Hamas rulers executed three convicted killers and dropped off their bullet-riddled bodies at a hospital Tuesday, despite appeals by human rights activists to halt the practice.

The U.N.'s top human rights official has said fair trials demanded under international law before the death penalty can be imposed are virtually impossible in Gaza. The Islamic militant group seized the Palestinian territory by force in 2007 and has established a regime that allows little dissent.

Hamas began carrying out formal executions in April, and Tuesday's killings brought the total number of prisoners put to death to five. In addition, rights groups say Hamas gunmen killed 17 prisoners, most suspected collaborators with Israel, during the chaos surrounding an Israeli offensive in the winter of 2008-2009.

The Hamas Interior Ministry said the men executed Tuesday were convicted killers.

One allegedly participated in the 2003 slaying of a young woman whose body was later tossed in a garbage bin. The killing provoked angry protests and calls from the public to execute the killers.

The other two men were accused of murdering money changers in two separate incidents.

"They will be examples to others," Interior Ministry spokesman Ihab Ghussein told local Gaza radio. "We don't want to terrorize citizens. We want to prevent more killing."

Following Arab tradition, the victims' families were contacted before the executions and asked if they would forgive the murderers, or accept compensation, Ghussein said. They refused, and the executions were carried out in front of the victims' families and Hamas officials.

The three bodies were dropped off at Gaza City's Shifa Hospital at dawn Tuesday, said a medical official. He spoke on condition of anonymity for fear of retribution.

Most Gaza residents appear to support the death penalty, but the executions were likely to deepen the international isolation of Hamas, branded a terrorist organization by the West.

Ghussein brushed off the criticism from rights groups. "We consider those who oppose these sentences to be inciting — even indirectly — to more crimes," he said.

Hamdi Shakour of the Gaza-based Palestinian Center for Human Rights said the executions were "the worst violation of the right to life."

The executions appeared to be an attempt by Hamas to demonstrate control over Gaza and burnish its law-and-order credentials. With Gaza under blockade by Israel and Egypt since 2007, the Hamas government has had little to show for three years in power, except its claim that it has restored security to the once chaotic territory.

The ministry did not say how many prisoners remain on death row. Some 40 other Gaza residents are on death row, said Samir Zakout of local rights group Mezan. Hamas officials could not confirm the numbers but said they intended to carry out more executions.

While Palestinian law allows the death penalty, execution orders require a signature by Palestinian President Mahmoud Abbas, but he only controls the West Bank. He has not sanctioned executions since taking power in 2005. Hamas does not recognize Abbas' rule and says it does not need his approval to implement the death penalty.

Gaza-based and international human rights groups have urged Hamas to halt executions, especially of suspected collaborators tried in military tribunals.