A British navy ship was evacuating British nationals from Libya on Sunday, the Ministry of Defence (MoD) said, with worsening security forcing thousands of people to flee.
The HMS Enterprise, which had been on a Mediterranean deployment, arrived off the capital Tripoli on Sunday, according to an MoD statement.
"A number of passengers were transferred to Enterprise by boat and given supplies for the journey," it added.
Britain is also planning to temporarily suspend its embassy operations in the troubled north African country, the Foreign Office (FCO) said.
A spokesman from the FCO said the majority of those being evacuated from Tripoli, believed to be around 100, were British.
Sunday's operation is likely to resemble one conducted in 2011 during the bloody uprising which ousted dictator Moamer Kadhafi, when a Royal Navy ship evacuated foreigners.
A launch protected by armed Royal Marines was expected to be sent into Tripoli port to collect the evacuees and ferry them to HMS Enterprise, a 91-metre (297-foot) long survey ship also designed to support amphibious operations.
Michael Aron, Britain's ambassador in Tripoli, said Friday he had "reluctantly" decided to leave due to the worsening local fighting.
Libya has suffered chronic insecurity since Kadhafi's overthrow, with the new government unable to check militias that helped to remove him and facing a growing threat from Islamist groups.
Fighting between the rival militias has forced the closure of Tripoli's international airport, while Islamist groups are battling army special forces in the eastern city of Benghazi.
In the past week, many countries have ordered their citizens to leave and, in some cases, have evacuated them.
Between 100 and 300 Britons are thought to be in Libya. Many British consular staff were evacuated last Monday.
"Fighting has intensified in Tripoli, including around the British embassy compounds," a Foreign Office spokesman said.
"In the light of the deteriorating security situation, we are taking steps temporarily to suspend operations at the British embassy in Tripoli after the planned assisted departure of British nationals," he said.
"We advise against all travel to Libya and urge British nationals in Libya to leave through commercially available means."