Gadhafi Sodomized and Tortured Before Being Killed: Human Rights Investigation Demanded (SHOCKING VIDEO)

The four-decade rule of Libyan autocrat, Col. Moammar Gadhafi finally came to an end on Thursday, after he was dragged from his hiding place - a drainpipe - in the town of Sirte and killed.

However, there is growing international unease about increasingly graphic and disturbing images of the abuse of a body that appears to be Gadhafi's, following his capture and the fall of his hometown of Sirte on Thursday.

"This latest massacre seems part of a trend of killings, looting and other abuses committed by armed anti-Gadhafi fighters who consider themselves above the law," said Peter Bouckaert, the Human Rights Watch researcher who investigated the killings.

Syrian-based Al-Rai TV station, which has served as a mouthpiece for the Gadhafi clan, said the dictator's widow, Safiya, also demanded an investigation. In a statement, according to ABC News, Gadhafi's son Saadi, who fled to Niger after the fall of Tripoli in August, said he was "shocked and outraged by the vicious brutality" shown towards his father and brother, Mutassim.

"I am proud of the bravery of my husband, Moammar Gadhafi, the holy warrior, and my sons who confronted the aggression of 40 countries over the past six months," the station quoted her as saying.

Meanwhile, 53 bodies discovered over the weekend were those of loyalists of the former Libyan leader, Human Rights Watch said. The group said fighters from Misrata were in control of the Hotel Mahari in Sirte, where the "badly decomposed" corpses were found.

Gadhafi was reportedly hiding like a "rat" in a drain tunnel when he was dragged out and killed by the Libyan fighters he once scorned, ironically, also as "rats". He was cornered, beaten and then shot in the head as Libya's new leaders declared they had overrun the last bastion of his long rule. A local military commander in Misrata told Reuters that when the "overenthusiastic" fighters came face to face with the man they hated the most, they took matters into their own hands.

"We wanted to keep him alive, but the young guys -- things went out of control," he said.

Meanwhile, a new video has sparked outrage across the world, over what is believed to be a gross violation of human rights. A frame-by-frame analysis of the video clearly shows a rebel trying to insert an object into Gadhafi's rear end.

It is not clear what the object was but Tracey Shelton, a correspondent for the GlobalPost, said it could either be a knife from the end of a gun (which Libyans call a "Bicketti") or a utility tool known as a Becker Knife and Tool (which is popularly known as a BKT).

A series of graphic videos have appeared since the death of Gadhafi, proving the leader was alive when captured.

Amnesty International, which has called for a "full, independent and impartial investigation" into his death, including pressing war crimes charges against the guilty parties if Gadhafi was executed, has also charged the rebels with mistreatment of detainees, including torture and lynching of captured pro-Gadhafi fighters. Both U.S. Secretary of State Hillary Clinton and UK Defense Secretary Philip Hammond have also called for a full investigation.