The chief prosecutor of the International Criminal Court said Monday he was assessing whether Libyan authorities can be tried for crimes against humanity against civilians calling for regime change.
Upon referral from the UN, his office was "assessing allegations of widespread or systematic attacks against the civilian population," Luis Moreno-Ocampo said in The Hague.
"This could constitute crimes against humanity and must stop," he added.
After the conclusion of this preliminary assessment, "within a few days", the office of the prosecutor would decide whether to launch a full investigation of alleged crimes committed since February 15.
This would allow the prosecution to "collect evidence and request an arrest warrant against those identified as the most responsible," said Moreno-Ocampo. "The judges will then decide on the evidence."
Libyan security forces have cracked down on protests that started nearly two weeks ago against the 41-year regime of Moamer Gaddafi.
The unrest has killed at least 1,000 people and set off a "humanitarian emergency", the UN refugee agency UNHCR said, as almost 100,000 people, mostly migrant workers, fled the North African state.
The UN Security Council on Saturday referred the situation in Libya to the ICC, saying "the widespread and systematic attacks currently taking place against the civilian population may amount to crimes against humanity."
"Information suggests that forces loyal to (Gaddafi) are attacking civilians in Libya," said Moreno-Ocampo.
"If people were in a square and were attacked by tanks, planes and soldiers, and if people were killed in a systematic way, this was a crime against humanity," he added, promising to move "swiftly and impartially".
"There will be no impunity for leaders involved in the commission of crimes."
The UN referral does not automatically result in an ICC investigation. Under the court's statute, the prosecutor first has to determine whether there is a reasonable basis for a full probe, which may lead to the issuing of arrest warrants and a trial.
Moreno-Ocampo said his office was liaising with the Arab League, the African Union, the UN's Human Rights Council, the UN High Commissioner for Human Rights and the UN secretariat, as well as certain governments, "in order to collect information required" in this initial phase.
"The office of the prosecutor is interested in receiving footage and images to confirm the alleged crimes," he said.
"Additionally, the office is liaising with Libyan officials and army officers to receive information about the identity of authorities with command and control over the organisations allegedly involved in the crimes."
The ICC is the world's only independent, permanent tribunal with the jurisdiction to try genocide, crimes against humanity and war crimes.
This is the second time that the UN Security Council refers a case to the ICC; the first, in 2005, concerned alleged human rights violations committed in Sudan's Darfur region.
That referral led to arrest warrants being issued in 2009 and 2010 against Sudanese President Omar al-Bashir for genocide, war crimes and crimes against humanity.
A UNSC referral is one of three ways that the ICC can open a probe. In the other cases before the ICC, the prosecutor has launched his own investigations or has had them referred by signatory states to the court's founding Rome Statute. Libya is not a signatory.