Moreno-Ocampo charted a timeline for Gadhafi's actions and sketched out a division of responsibility among the Libyan ruler, his son Seif Islam, and brother-in-law Abdullah Sanoussi, who is married to Gadhafi's second wife's sister and is head of military intelligence.
The court, in the Hague, Netherlands, will take at least three weeks before ruling, Moreno-Ocampo said in an interview. But his move was certain to please NATO, which is conducting a bombing campaign under a U.N. mandate to protect Libyan civilians.
The move might increase pressure on Gadhafi to think about finding refuge in a country that has not agreed to ICC jurisdiction, said David Scheffer, a Clinton administration envoy for war crimes who now teaches international law at Northwestern University.
Moreno-Ocampo called the evidence against Gadhafi overwhelming and added that his investigation was authorized by a U.N. Security Council resolution.
The prosecutor said he had interviewed Libyans who had fled the country, including eyewitnesses who could testify to instructions given by Gadhafi, Seif Islam, and Sanoussi to kill and imprison protesters.
In Tripoli, a Gadhafi spokesman said the court had reached "incoherent conclusions."
"We have never, in any stage of the crisis in Libya, ordered the killing of civilians or hired mercenaries against our people," spokesman Moussa Ibrahim said.
The Libyan government has "long requested fact-finding missions, international observers, and experts to counterbalance the biased and inaccurate media reports about events in Libya. No one listened," Ibrahim said.
People in rebel-held areas said it was high time the court acted.
"Gadhafi destroyed our city, he killed our children, and he fought us with all kinds of weapons, so what is the meaning of the request or a report saying Gadhafi is a criminal?" said Aiman Abu Shama, a doctor in the besieged western port of Misrata. "Everybody knows that he has to be arrested."
The prosecutor's office described Seif Islam as his father's "de facto prime minister," who also played a leading role in bringing foreign mercenaries to Libya. It branded Sanoussi as the Libyan leader's "right-hand man" and "executioner."
The prosecutor said Gadhafi tried to avoid creating a paper trail by giving orders verbally through a special institution called the Information Bureau of the Leader.