Over 250 Gaddafi supporters have been found dead in Sirte less than a week after the capture and killing of the dictator.
The bodies were discovered over the last couple of days in Sirte, where Gaddafi was killed, and it's suburbs, according to a local newspaper. Most of the people found dead were loyal supporters of the Gaddafi regime.
Officials of the National Transitional Council (NTC) have promised to perform an investigation to find and punish those who took part in the killings.
Bodies have been discovered all over Libya since the death of Colonel Gaddafi.
Fifty-three decomposed bodies were found in the garden of a hotel in Sirte. Human Rights Watch said the victims were Gaddafi supporters and were executed.
Another 10 decomposed bodies were found at a different location in Sirte. Human Rights Watch could not determine whether they were bodies of pro-Gaddafi or anti-Gaddafi forces. It appears those people were also executed.
The Human Rights Watch has put pressure on the transitional government to investigate the killings.
Peter Bouckaert, emergencies director at Human Rights Watch, said Monday, "The evidence suggests that some of the victims were shot while being held as prisoners, when that part of Sirte was controlled by anti-Gaddafi brigades who appear to act outside the control of the National Transitional Council (NTC)."
"If the NTC fails to investigate this crime it will signal that those who fought against Gaddafi can do anything without fear of prosecution," he added.
Muammar Gaddafi was killed in Sirte last Thursday after spending weeks on the run. Videos of his capture have surfaced and have gone viral.
Gaddafi was the de facto leader of Libya for 42 years after taking power in a military coup.
His body was buried in a secret desert location Tuesday after days on public display.