BENGHAZI, Libya (Reuters) - The International Criminal Court has evidence Muammar Gaddafi's government planned to put down protests by killing civilians before the uprising in Libya broke out, the ICC's prosecutor said on Tuesday.
The peaceful protests that erupted on February 15 descended into civil war as Gaddafi's forces first fired on demonstrators, then violently put down the uprisings that followed in the west, leaving the east and the third city of Misrata in rebel hands.
NATO-led air power is now holding the balance in Libya, preventing Gaddafi's forces overrunning the seven-week old revolt, but unable for now to hand the rebels outright victory.
The United Nations Security Council, which on March 17 sanctioned air strikes on Libyan government forces to prevent them killing civilians, in February referred Libya to the ICC, the world's first permanent war crimes court.
Court prosecutor Luis Moreno-Ocampo is to report back to the U.N. on May 4, and is then expected to request arrest warrants.
"We have evidence that after the Tunisia and Egypt conflicts, people in the (Gaddafi) regime were planning how to control demonstrations in Libya," Moreno-Ocampo told Reuters in an interview.
"The shootings of civilians was a pre-determined plan," he said, adding the plan started to be developed in January.
The court prosecutor wants to speak to former Libyan Foreign Minister Moussa Koussa who defected to Britain last week, saying he did so because of attacks on civilians by Gaddafi's forces.
Koussa's defection would be taken into consideration in the investigation into Gaddafi, his sons and aides, Moreno-Ocampo said, hinting others inside the government might follow suit.
"The fact that Moussa Koussa defected is interesting because that is one option you have. If you have no power to stop the crimes then you can defect to show you are not responsible," he said.
Fighting on the frontline in the eastern oil terminal town of Brega has become bogged down with Gaddafi's advantage in tanks and artillery canceled out by NATO-led air strikes which effectively back the rebels.
Diplomatic efforts to end the conflict have similarly failed to make any progress with the government side offering concessions, but insisting Gaddafi stay in power and the rebels adamant that Libya's leader for the past 41 years leave.
After a series of rapid rebel advances followed by headlong retreats, the insurgents have held their ground for six days now in Brega, putting their best trained forces in to battle for the town and keeping the disorganized volunteers away.
A familiar pattern has set in, with lightly armed volunteers pulling back under rocket fire and better-trained rebel soldiers, most of them from army units that defected from Gaddafi or came out of retirement, tending to hold their ground.
As two government trucks mounted with heavy machine guns lay smoldering from an allied air strike, machinegun fire was heard in the west of the sparsely populated desert settlement then rockets landed near a group of rebels waiting with machine gun mounted pick-up trucks at the town's eastern gate.
Rockets zipped back toward Brega from a rebel position near the entrance to its eastern residential zone, but as more government ordinance rained down, scores of rebels leapt into their pick-ups and sped off once again into the desert.
"It's back and forth," said a rebel officer who did not give his name. "The clashes are continuing between the industrial area, the company and the residential area."
The rebels appear to be set for a boost with the arrival of a tanker in one of their ports which can carry 1 million barrels of crude, worth more than $100 million, which would be their first shipment since the fighting broke out.
That will help the rebel leadership to pay salaries and bolster its image as a potential government.
Rebel leaders say Qatar has agreed to market oil from east Libyan fields after the Gulf state recognized the revolutionary council in Benghazi as Libya's legitimate government.
In the capital Tripoli, angered by fuel shortages and long queues for basic goods caused by sanctions and air strikes, some residents began openly predicting Gaddafi's imminent downfall.
The government offered concessions. Spokesman Mussa Ibrahim said Libya was ready for a "political solution" with world powers and offered a "constitution, election, anything. But the leader has to lead this forward."
Libyan Deputy Foreign Minister Abdelati Obeidi ended a trip to Greece, Turkey andMalta to set out the government position.
Turkey is expecting an envoy to visit from the opposition in the coming days and is listening to both sides.
"Both sides have a rigid stance," a Turkish Foreign Ministry official said after Obeidi's visit. "One side, the opposition, is insisting that Gaddafi should go. The other side is saying Gaddafi should stay. So there is no breakthrough yet."
(Additional reporting by Alexander Dziadosz in Brega, Aaron Gray-Block in The Hagueand Ibon Villelabeitia in Cairo; Writing by Jon Hemming; Editing by Giles Elgood)