Britons still in Libya are being urged to leave on the final government-chartered flight from Tripoli later.
There are thought to be fewer than 500 Britons left in Libya, many of them oil workers in desert regions.
Foreign Secretary William Hague said the rescue operation was about to enter its final phase, but there was still concern over the isolated oil workers.
The Foreign Office says it has helped about 600 British nationals to leave the crisis-hit North African country.
Reports say anti-government protesters have faced heavy gunfire in the capital Tripoli, as the Libyan leader Colonel Muammar Gaddafi defies calls for him to stand down.
Fighting has raged for the past week between anti-government forces and pro-Gaddafi troops and militiamen in towns and cities outside the capital.
‘Way out’
On Monday, Mr Hague will attend the UN Human Rights Council in Geneva as part of international efforts to end the violence.
In a statement, he said: “The message is clear: that there will be a day of reckoning for those guilty of the appalling atrocities. The world will act together to hold them to account.”
He said there had been “gross and systematic human rights violations by the Libyan authorities”.
Earlier, Mr Hague said as well as Saturday’s last flight, the Royal Navy frigate HMS Cumberland would return to Benghazi, Libya’s second largest city, to pick up more evacuees, probably on Sunday.
“There are now very few British nationals remaining in Tripoli. It’s very important that those that remain go to the airport, that they do so at first light [on Saturday],” he said, adding that Saturday would see the last government chartered plane leave Tripoli.
“For.. anyone else who can get to Benghazi, HMS Cumberland will return probably on Sunday. I want them to know that they do have a way out.”
With regards to those stranded in desert locations, Mr Hague added: “We are doing a lot of work on how we can help them. We can’t say anything more about that at the moment.”
The Foreign & Commonwealth Office (FCO) has given details of flights returning British nationals to the UK:
- A flight chartered by oil company BP carrying 79 Britons landed at Gatwick airport on Thursday morning
- An FCO-chartered flight carrying 181 adults and two children, including 113 Britons, landed at 2030 GMT on Thursday
- Another FCO-chartered flight arrived at Gatwick at 0315 GMT on Friday, carrying 130 people including 53 Britons
- A charter flight carrying three Britons arrived at Stansted airport at 0530 GMT
- A charter flight which left Tripoli at 1630 GMT, arrived at Gatwick at 1954, carrying 34 Britons, 18 Canadians and 27 other nationals
Some 49 British nationals have also departed on a US ferry from Tripoli harbour.
HMS Cumberland has picked up 207 people including 68 British nationals from Benghazi and is due to arrive in Malta on Friday night, where evacuees can pick up flights to the UK.
An FCO spokesman said: “We are doing all we can to get [British nationals] out of Libya, drawing on both military and commercial assets, as well as working with international partners.”
The FCO said it had helped directly about 450 British nationals to leave Libya, and facilitated the departure of another 150.
It added that information from British companies indicated there may be more than the 170 British workers in remote desert camps previously thought, but it would not be drawn on the exact number for “security reasons”.
British Airways and fellow UK carrier bmi, which both usually operate daily flights between Heathrow and Tripoli, have cancelled their Libya services up to and including Monday.
Prime Minister David Cameron has apologised for the speed of the government’s response to the crisis in Libya and said lessons would be learned.
Labour leader Ed Miliband said: “There is a worrying whiff of incompetence about the way this government is handling this issue, and it’s become a pattern with this government about the way decisions are made and the way things are handled.
