David Cameron: Remember Colonel Gaddafi Libya victims
David Cameron has said it is a day to remember Col Muammar Gaddafi's victims after Libya confirmed the country's former leader had been killed.
The prime minister said people in Libya now had an even greater chance to build a strong and democratic future.
Libya's transitional authorities said Col Gaddafi died after an assault by its forces on his home town of Sirte.
UK forces have been part of Nato-led operations targeting Gaddafi regime positions to protect Libyan civilians.
Meanwhile the Scottish government has said it is ready to re-open the investigation into the Lockerbie bombing, saying the Libyan intelligence agent who was convicted "did not act alone".
In the evening, Libyans gathered outside the country's embassy in London and on streets in Manchester - home to the UK's largest expatriate community - to mark the news.'Brutal dictator'
Speaking outside Number 10, Mr Cameron said: "I think today is a day to remember all of Colonel Gaddafi's victims, from those who died in connection with the Pan Am flight over Lockerbie, to Yvonne Fletcher in a London street and obviously all the victims of IRA terrorism who died through their use of Libyan Semtex.
"We should also remember the many, many Libyans who died at the hands of this brutal dictator and his regime."
Robin Chrystal, BBC News
Ordinary Libyans in London say they are happy Col Gaddafi is dead, and excited about the future.
"It's a great day for every Libyan. Finally, finally he has gone!" said Nadar Halab. "I know lots of people who died at his hands. Now I can take my wife and baby daughter home for the first time".
Today Mr Halab travelled to London to get a visa for his English wife Michelle and three-month-old daughter Lana.
"I was in the embassy when the news came through. It's ironic. I was technically in Libya."
Civil engineer Akrum Mshaya says he won't really believe Colonel Gaddafi is dead until he sees the video evidence.
"I'm 30, I've spent my whole life living under that murderer, I want to believe it but I need to be sure.
"I want to go back, I will go back, we must forget the past and build a new future."
The prime minister added: "People in Libya today have an even greater chance, after this news, of building themselves a strong and democratic future.
"I'm proud of the role that Britain has played in helping them to bring that about and I pay tribute to the bravery of the Libyans who have helped to liberate their country.
"We will help them, we will work with them, and that is what I want to say today."
Mr Cameron said the Libyan transitional authority's acting Prime Minister Mahmoud Jibril confirmed that Col Gaddafi was dead.
Foreign Secretary William Hague said Libya could now "move on to the next phase".
"It brings much closer the end of the Nato mission... I think we will want to be sure there are not other pockets of pro-Gaddafi forces still able to threaten the civilian population."
Mr Hague later told Channel 4 News that it would have been better had Col Gaddafi not been killed once he was caught.
"We would have preferred him to be able to face justice at the International Criminal Court or in a Libyan court for his crimes. We don't approve of extra-judicial killings", he said, amid reports that Col Gaddafi was shot after being captured alive.'Ready to investigate'
Shadow foreign secretary Douglas Alexander said: "This is a momentous day in the history of Libya, and closes a dark 42-year-long chapter in the country's history.
"All of us will hope this will also mark an end to the present fighting in Libya, but the challenges facing the NTC remain great."
The Scottish government said it would probe any new leads surrounding the Lockerbie bombing in 1988, should information come to light following the developments in Libya.
A spokesman said: "The only person convicted, [Abdelbaset Ali] al-Megrahi, acted in his capacity as a Libyan intelligence agent - he was found guilty of an act of state-sponsored terrorism and did not act alone.
"Therefore, our police and prosecution authorities stand ready to investigate and follow any new lines of inquiry that may be emerging in Libya at the present moment."
The spokesman added: "We now look forward to the end of conflict in Libya, and the emergence of a free and democratic country."
Scotland's First Minister Alex Salmond said: "Gaddafi was a brutal dictator, who exploited his country and brutalised the Libyan people for over four decades - he lived by the sword, and has met his just-deserts."
The Ministry of Defence in London confirmed Nato warplanes attacked a convoy of vehicles fleeing Sirte on Thursday.
An MoD spokesman said: "The convoy was targeted on the basis that this was the last of the pro-Gaddafi forces fleeing Sirte."
UK fighter planes were not involved in the attack although RAF aircraft have been flying reconnaissance missions over Libya on Thursday.
The International Criminal Court had been seeking Col Gaddafi's arrest for crimes against humanity after he was toppled in August following 42 years in power.
Mr Cameron has said the RAF carried out around a fifth of all strike sorties against forces loyal to Col Gaddafi, while HMS Liverpool shelled positions in Sirte during the city's siege.