Foreign Secretary Boris Johnson has described how officials worked through the night helping British people caught up in the crisis in Turkey.
The attempted military coup and unrest is believed to have left more than 250 dead and 1,440 injured, with 2,839 military personnel detained by the authorities.
Mr Johnson's comments came as the Government's Cobra emergency committee prepared to meet on Sunday morning.
The former Mayor of London, who is only days into his new job, said the Foreign Office was "in what Her Majesty's Diplomatic Service calls 'crisis mode'" when he arrived there on Saturday morning.
He said "dozens of people had been up all night, calmly monitoring screens and coolly assessing fresh information", and some of them had worked consecutive shifts without sleep as they dealt with the needs of UK nationals abroad.
In a column in the Sunday Express, Mr Johnson, who has Turkish ancestry, wrote: "Most of the officials - as you would expect - were working on the unfolding crisis in Turkey, where the failed coup had myriad implications for this country.
"To take one example: at about 3am yesterday morning we realised that there was a party of British passengers who were changing planes at Istanbul's massive Ataturk airport.
"They were stuck airside as the coup attempt began, and their onwards flight was grounded. Turkish president Erdogan was apparently planning to land at that airport and restore his authority. What if the rebels decided to attack the airport?
"Someone needed to get through to the party and, as so often happens, the UK happened to have a diplomat on the spot. A UK official also transiting through the airport and trapped airside at Istanbul was able to meet up with the party and provide an immediate link to London.
"Elsewhere in Turkey - at the resorts and the big transport hubs - UK consular staff were out, many in hi-vis jackets, providing information and travel advice, just as they had been doing in Nice only hours earlier.
"As I talked by teleconference first to the Turkish foreign minister and then to our staff in Istanbul and Ankara, I was filled with amazement at the reach and reputation of this country around the world."
Meanwhile, the Cobra emergency committee will meet on Sunday morning and officials have agreed to keep travel advice to the country "under review".
Downing Street said the National Security Adviser chaired a meeting of senior officials on Saturday to discuss the potential repercussions as the Turkish government began cracking down on its opponents.
The Turkish government purged 2,745 judges seen as loyal to an exiled cleric the country's president blames for the failed coup.
The Foreign Office updated its travel advice, saying the situation appeared to be calming but remained potentially volatile.
Consular staff are continuing to provide assistance to those affected by airport closures and Foreign Office staff are in close contact with the UK's largest travel association Abta.
Britons were advised to avoid public places, in particular demonstrations, and remain vigilant, although the country's coastal resorts did not appear to be significantly affected.
Flights to and from Turkish airports were "returning to normal", the Foreign Office said.
US president Barack Obama pledged to work with the Turkish government to help maintain safety and called on it "to act within the rule of law" and avoid actions leading to further instability.