TUNIS (Reuters) - The United Nations has said it is “appalled” by apparent retaliatory killings in Libya following reports of eight bodies found in the eastern cities of Benghazi and Derna.

Five bodies were found in Benghazi’s Laithi neighborhood on Friday, residents told Reuters. Pictures posted on social media appeared to show the bodies, bloodied and mutilated, lying in the dirt.

The pictures could not be independently verified, and security officials in Benghazi declined to comment.

In Derna, 250 kilometers (155 miles) east of Benghazi, the bodies of three people who appeared to have been summarily killed were found dumped in the city on Thursday, medical sources said.

“UNSMIL is appalled by new reports of retribution killings in Libya,” the U.N.’s Libya mission, UNSMIL, said on its Twitter account.

“The brutal pattern of violence must end. Those in effective control of fighters and those ordering, committing such crimes are liable under international law.”

The reports came after a twin car bombing in Benghazi left 35 people dead and dozens injured on Tuesday, and on Wednesday pictures and video emerged purporting to show the summary execution of 10 prisoners outside the mosque where the bombing took place.

Benghazi is controlled by the Libyan National Army (LNA), the dominant force in eastern Libya. It is led by Khalifa Haftar and fought Islamists and other opponents in Benghazi from 2014 until late last year as part of a wider conflict that developed in Libya after a 2011 uprising.

Notes had been left with the bodies found in Benghazi accusing the victims of militant Islamist loyalties, said residents, who did not want to be named for security reasons.

There have been a number of cases of bodies with gunshot wounds and showing signs of abuse found in Benghazi in areas under LNA control.

In Derna, the LNA has long been battling the Derna Mujahideen Shura Council (DMSC), an armed alliance that controls the city.

The DMSC said it had arrested three people earlier this week for allegedly plotting attacks on behalf of the LNA. A Derna resident said the three were the same men whose bodies were found on Thursday.

The DMSC did not immediately respond to a request for comment.

(This version of the story has been refiled to fix typo in headline)