GAZA CITY, Gaza Strip (AP) — Gaza's Islamic militant Hamas rulers said Wednesday they intend to execute residents convicted of murder even without the needed approval of the Palestinian president.

Hamas lawmakers "endorsed" 13 death sentences after mounting pressure from victims' families. West Bank-based President Mahmoud Abbas has refused to approve the Hamas verdicts and the United Nations' High Commissioner for Human Rights says he is deeply concerned over the imminent executions.

"The Gaza authorities' statements follow the demands of several families for the death penalty to be carried out against individuals accused of killing their relatives," a spokesman for the commissioner, Rupert Colville, said. "Death sentences may only be carried out in extremely limited circumstances, and pursuant to a trial and appeals that scrupulously follow fair trial standards. We have serious doubts as to whether capital trials in Gaza meet these standards."

Human Right Watch also condemned the announcement.

"The death penalty is an inherently cruel and irreversible punishment in all circumstances," said Sari Bashi, Israel and Palestine director at Human Rights Watch, in a statement. "But it's particularly egregious to execute defendants sentenced in Gaza, whose court system is rife with coercion, torture and compromised procedures."

The Palestinians have been divided since 2007 when Hamas ousted forces loyal to Abbas' forces from Gaza in bloody street battles. Despite a 2014 reconciliation agreement, Hamas remains in control of Gaza.

During a 2014 war with Israel, Hamas carried out the extrajudicial killings of 23 alleged spies. It also has executed 19 people convicted of murder or collaboration with Israel since 2007.

The HRW statement noted that the collaboration charge is particularly worrisome, saying that in the absence of due process the charge, "can be used to settle personal or political scores."