The United Nations human rights office called on Friday for a full investigation into the death of Libyan leader Muammar Gaddafi, Reuters reports.

"It is unclear how he died. There is a need for an investigation," UN human rights spokesman Rupert Colville told a news briefing in Geneva.

Referring to separate cell phone images showing a wounded Gaddafi first alive and then later dead amidst a jumble of anti-Gaddafi fighters after his capture in his hometown of Sirte on Thursday, he added: "Taken together, they were very disturbing."

An international commission of inquiry, launched by the UN Human Rights Council, is already investigating killings, torture and other crimes in Libya.

Colville said he expected that the team would look into the circumstances of Gaddafi's death.

"It is a fundamental principle of international law that people accused of serious crimes should if possible be tried. Summary executions are strictly illegal. It is different if someone is killed in combat," he told Reuters Television.