GENEVA, Dec. 23 (Xinhua) -- The UN human rights office on Wednesday said it is deeply concerned by the recent U.S. presidential pardons for four security guards from the private military firm Blackwater who were convicted of killing 14 Iraqi civilians.

In a statement issued Wednesday, Marta Hurtado, spokesperson for the Office of the UN High Commissioner for Human Rights, commented that pardoning them contributes to impunity and has the effect of emboldening others to commit such crimes in the future.

The statement stressed that these four individuals were given sentences ranging from 12 years to life imprisonment, including on charges of first-degree murder.

"By investigating these crimes and completing legal proceedings, the U.S. complied with its obligations under international law," the statement said, adding that victims of gross human rights violations have the right to see perpetrators receive punishments proportionate to the severity of their conduct.

The UN human rights office calls on the United States to renew its commitment to fighting impunity for gross human rights violations and serious violations of international humanitarian law, as well as to uphold its obligations to ensure accountability for such crimes.

According to media reports, U.S. President Donald Trump on Tuesday granted full pardon to 15 people, including four Blackwater security guards convicted of killing 14 Iraqi civilians.