Moamer Kadhafi's family plans to file a war crimes complaint against NATO with the International Criminal Court (ICC) for the alliance's alleged role in his death, the family's lawyer said Wednesday.

The 69-year-old ex-leader was captured and killed Thursday near the city of Sirte in circumstances that are still unclear, but it has been confirmed NATO aircraft fired on pro-Kadhafi vehicles driving in a convoy from the city.

Marcel Ceccaldi, a French lawyer who previously worked for Kadhafi's regime and now represents his family, told AFP that a complaint would be filed with the Hague-based ICC because NATO's attack on the convoy led directly to his death.

"The wilful killing (of someone protected by the Geneva Convention) is defined as a war crime by Article 8 of the ICC's Rome Statute," he said.

He said he could not yet say when the complaint would be filed, but said it would target both NATO executive bodies and the leaders of alliance member states.

"Kadhafi's homicide shows that the goal of (NATO) member states was not to protect civilians but to overthrow the regime," Ceccaldi said.

"Either the ICC intervenes as an independent and impartial jurisdiction or it doesn't, in which case force will overrule the law," he said.

Libya's ruling National Transitional Council has announced an investigation into Kadhafi's death.

International disquiet has grown over how Kadhafi met his end after NTC fighters hauled him out of a culvert where he was hiding following NATO air strikes on the convoy in which he had been trying to flee his falling hometown.

The ICC in June issued arrest warrants for Kadhafi, his most prominent son Seif al-Islam and the former regime's intelligence chief Abdullah al-Senussi, for "crimes against humanity" committed by troops under their orders, using "lethal force" to quell the uprising against his regime.

Local officials said Tuesday that Seif and Senussi, who have so far evaded capture, were poised to cross into Niger where they were expected to seek refuge along with other former regime officials.