The Security Council had imposed sanctions on Gaddafi and referred Libya's crackdown on protests to the ICC [Reuters]

The prosecutor of the International Criminal Court has said he will open a formal investigation into possible crimes against humanity in Libya.

Luis Moreno-Ocampo, the ICC prosecutor, decided to launch the investigation on Wednesday after a "preliminary examination of available information."

The announcement was an unprecedentedly swift reaction to the violent crackdown on anti-government protests by Muammar Gaddafi, the Libyan leader, and his supporters.

Prosecutors often take months and sometimes years to decide whether to open an investigation into possible war crimes.

The ICC has previously said that it has been in contact with Libyan army officers to gather information about civilian deaths during the uprising and pledged "no impunity" for anyone found to have committed crimes against humanity.

"Information suggests that forces loyal to President Muammar Gaddafi are attacking civilians in Libya. This could constitute crimes against humanity and must stop,” Moreno-Ocampo said on Tuesday.

"There will be no impunity for leaders involved in commission of crimes," he said.