Thousands of Libyans have turned out to cheer UK Prime Minister David Cameron and French President Nicolas Sarkozy in the eastern city of Benghazi.
“It is great to be in free Libya,” Mr Cameron said. “Col Gaddafi said he would hunt you down like rats, but you showed the courage of lions.”
Earlier, the two met Libya’s interim leader in Tripoli and pledged their support for the new authorities.
They also promised to unblock more frozen Libyan assets.
After the talks in Tripoli, the two leaders travelled under heavy security to Benghazi, where a crowd had gathered in central Liberty Square, waiting to hear them speak.
Shouting to make himself heard above the roar of welcome, Mr Cameron told his audience : “Your friends in Britain and France will stand with you as you build your country and build your democracy for the future.”
Mr Sarkozy plunged into the crowd, reaching across his bodyguards to shake the hands of waiting Libyans, many of them waving French flags.
This is the first visit to Libya by Western leaders since ex-leader Col Muammar Gaddafi was overthrown last month.
Earlier, Mr Cameron praised the National Transitional Council (NTC) for the way it has established control over the country, but warned that the “hardest part” was still to come.
Both he and Mr Sarkozy said Nato would continue its mission under a UN mandate to protect Libyan civilians until the last remnants of pro-Gaddafi forces were defeated. Britain and France were at the forefront of the Nato operation in Libya.
“The message, I think, to Gaddafi and all those holding arms on his behalf is: it is over. Give up. The mercenaries should go home,” Mr Cameron told a news conference in Tripoli.
NTC chief Mustafa Abdul Jalil thanked them for taking “brave positions” during the Libyan uprising.
“They showed us political, economic and military support which helped the rebels establish a state, and we thank France and the UK for that,” he said.
Mr Sarkozy urged Libyans to avoid “vengeance and retaliation”, calling on them to preserve unity and seek reconciliation.