In a series of developments:
• Witnesses in Tripoli told of deaths at mosques and of armed men around the city. Elsewhere in the country, pro-Gaddafi forces were said to have fired on civilians from helicopters.
• The Sunday Telegraph met captured African mercenaries who Col Gaddafi had paid to prop up his regime, including a 16-year-old boy handed a gun and then told to go out and massacre protesters.
• Billions of pounds of Libyan assets are set to be frozen in Britain, including shareholdings in a major publishing company and large amounts of property.
• The Government is pushing for an arms embargo, a travel ban and a war crimes investigation into the crackdown on demonstrators, which appears to be reaching new heights of brutality.
Ban Ki-moon, the UN Secretary General, suggested yesterday that 1,000 or more had died since the rebellion against Col Gaddafi's 42-year rule began last week.
David Cameron, the Prime Minister, and Mr Hague held talks over the phone with a series of world leaders yesterday including those of France and Russia, after which officials made clear that the brutality of the Gaddafi regime "would not be tolerated". President Barack Obama said Gaddafi had “lost the legitimacy to rule” and should step down immediately.
In a separate move, The Sunday Telegraph understands that British diplomats have privately urged Nato and the UN to start thinking about the possibility of imposing a no-fly zone.
Humanitarian specialists were also on the ground in Egypt and making their way to the Libyan border, officials said.
The team were assessing how Britain and the international community could best assist the region as the situation worsens. "We are monitoring the movement of refugees from Libya to Tunisia and Egypt," a spokesman said.
The stance reflects a significant toughening of the British Government's position after an initially slow response to the crisis. Ministers faced criticism for a sluggish response to the need for evacuation but rescue efforts have sped up in recent days.
As diplomatic efforts to remove Col Gaddafi intensify, Mr Hague will meet Hillary Clinton, the US Secretary of State, to discuss the crisis tomorrow.
The rescues took place south of Benghazi, which has fallen to the rebels, and involved members of the SAS and SBS and support troops.
The Hercules aircraft, believed to be from RAF 47 Squadron (Special Forces Flight), flew from a base on Malta where they had assembled on Friday as concern grew about the safety of the British workers.
SAS and SBS units are on standby to evacuate more Britons.
A final evacuation by the frigate HMS Cumberland is expected early this morning when it docks at Benghazi for any remaining Britons.
Liam Fox, the Defence Secretary, revealed the mission after the two planes landed in Malta shortly after 6pm last night.
"I can confirm that two RAF C130 Hercules aircraft have evacuated around 150 civilians from desert locations south of Benghazi,” he said. “HMS York has arrived in Valletta to take on board stores so it can assist the evacuation effort if required.
“And a number of other military assets remain available to support the FCO [Foreign and Commonwealth Office] led efforts to return civilians from Libya.”
The majority of the 150 civilians rescued were British but other nationalities were also plucked to safety.
During the mission, two RAF Hercules, which can carry up to four heavily armed SAS Land Rovers, landed on improvised desert airstrips.
There were reports that Special Forces personnel were landed in Libya by HMS Cumberland when it docked in Benghazi on Thursday and fanned south into the country’s desert. They picked Britons, almost all of whom had barricaded themselves in compounds around the Libyan desert as law and order collapsed.
Many had said they were living in fear of their lives and had been faced with armed looters, while some had been robbed at gunpoint.
The wives of some of the stranded men had complained about a lack of action by the Foreign Office - although they could not be warned of plans for the rescue in order to keep it secret.
In New York, the noose tightened on the Libyan dictator as world powers finalised plans at the United Nations for financial and weapons sanctions against his clan and key regime officials.
The US pressed ahead with its own sanctions in tandem with the international effort, aiming to peel away remaining members of Col Gaddafi’s inner circle after several high-profile defections last week.
If the embattled Libyan leader is not brought down by a coup, then his fate seems set to be determined by a bloody showdown for his base in the capital. Much of the rest of the country is either occupied by rebels or under no control.
Helicopter-borne pro-Gaddafi mercenaries fired on protesters attending a funeral in the western city of Misurata, a witness said. With the sound of heavy weapons fire audible in the background, he said the fighters opened fire on mourners outside a mosque in the city, 90 miles east of the capital.
Residents of Tripoli said they had seen Gaddafi followers leaving the regime’s Revolutionary Committee headquarters armed with newly-issued weapons.
Others reported pro-Gaddafi militiamen wearing green headbands being driven through the city by trucks and manning roadblocks to control movement.
The capital remained quiet for much of the day after the bloodshed on Friday when pro-Gaddafi security forces opened fire on the largest anti-government marches in the city since the revolt broke out.
In Tripoli’s Tajoura district, a hub of anti-regime protests, residents barricaded streets with concrete blocks and chopped-down palm trees to keep out vehicles filled with young pro-Gaddafi fighters wielding automatic weapons.
Saif al-Islam, Col Gaddafi’s son, told foreign journalists invited on a government propaganda tour that the capital was “calm” and there were no casualties there.
“Everything is peaceful,” he said. “Peace is coming back to our country.” He insisted that the regime wanted negotiations with the opposition and said there were nothing more than “minor problems” in the cities of Misurata and Zawiya, where “we are dealing with terrorist people”.
The spectre of a bloodbath in Tripoli was hanging over world diplomats as they met for an unusual Saturday session to discuss a British-French plan for an immediate arms embargo, freezing of assets and travel ban on the Gaddafi family and senior government figures.
The US moved quickly to impose its own sanctions on Libya, with President Obama issuing an executive order to freeze assets and ban weapons sales.
In a symbol of Col Gaddafi’s loosening grip on power, the “busty” Ukrainian nurse revealed to have been the dictator’s constant companion was said to be returning to her family in Europe.