Hamas, the Islamist movement in de facto control of the Gaza Strip, says it plans to conduct a series of public executions in the Palestinian territory.
Hamas legislators said Wednesday that they had agreed to the plans by the group, which seized the Gaza Strip in June 2007 from Palestinian President Mahmoud Abbas' forces.
Previously, capital punishment had only been carried out with approval from Abbas, who remains in control of the West Bank.
The Palestinian Legislative Council, the parliament for the Palestinian territories, has not met since Hamas' takeover in Gaza, and it was not clear what authority the Hamas legislators had to authorize the executions.
The Abbas government called the execution plans illegal.
Ismail Jaber, chief prosecutor for the Hamas regime in Gaza, said 13 prisoners were facing death.
In New York, the United Nations on Wednesday urged Hamas not to carry out the executions and called on Abbas to establish a moratorium on capital punishment. The executions might begin imminently, top UN officials warned.
Hamas held a majority in the Palestinian Legislative Council in 2007, but no elections have been held since the Gaza takeover, despite multiple attempts at reconciliation with Abbas and the Fatah faction that he leads.
Nickolay Mladenov, UN special envoy for the Middle East peace process, told the UN Security Council that under international law, the death penalty can be applied only for the most serious crimes and after processes that "scrupulously follow fair trial standards."
"I have serious doubts as to whether capital trials in Gaza meet these standards," Mladenov said.
Earlier in Geneva, a spokesman for UN High Commissioner for Human Rights Zeid Ra'ad al-Hussein warned that public executions were prohibited under international human rights law.
"We urge the authorities in Gaza to uphold their obligations to respect the rights to life and to a fair trial ... and not carry out these executions," said Rupert Colville, Zeid's spokesman.