Flights out of Istanbul's Ataturk Airport have been suspended while flights bound for Turkey are being diverted to other nearby countries or are returning to their origin.
There are reports the military have blocked access to Ataturk Airport.
A British Airways flight to Istanbul has diverted to Sofia, Bulgaria, and a Lufthansa flight to Istanbul is returning to its origin in Frankfurt, company spokeswomen told Reuters.
The U.S. Federal Aviation Administration said all US inbound flights from Istanbul that were in the air prior to the airport's closing would be allowed to land in the United States as planned.
Turkish Airlines and other carriers did not immediately comment.
Qatar Airways said all airport in Turkey remained closed and passengers travelling on flights to Turkey were advised to check their flight status.
Russian airline Aeroflot has also reportedly announced it had cancelled all flights to Turkey.
Saudi Airlines said: 'Due to current situations in, all SAUDIA are suspended until further notice.'
Airports around the world are advising passengers to contact their airlines to find out about their flights.
'If you're due to fly to Turkey imminently, it's best if you check directly with you airline for information on flights,' London's Gatwick Airport tweeted.
UK Foreign Secretary Boris Johnson tweeted: 'Very concerned by events unfolding in. Our Embassy is monitoring the situation closely. Brits should follow FCO website for advice.'
The Foreign and Commonwealth Office tonight said it was aware of the developments but was still 'urgently' seeking more information from on the ground.
'We are aware of the current developments in Turkey,' the FCO's updated travel advice said.
'We are urgently seeking more information.
'Until the situation becomes clearer, we advise you to avoid public places and remain vigilant.'
The US State Department has issued a similar advisory note, urging its citizens to contact familiy and friends to let them know they were safe.
'We encourage U.S. citizens to shelter in place and do not go the U.S. Embassy or Consulates at this time,' the department said.
'Monitor local press for updates, avoid areas of conflict, and exercise caution if you are in the vicinity of any military or security forces.'
Turkey has been plagued by attacks in recent months, but Brits have still been travelling to the country.
Flight tracking website FlightAware.com so far listed 33 canceled departures for Friday and Saturday.
This was the latest shock to tourism in Turkey, which has taken a hit from a number of bombings this year, including a suicide attack in June that killed 45 people at Istanbul's main airport.
Popular destinations among holidaymakers are the city of Istanbul and areas along Turkey's Mediterranean coast.
It is unclear whether last night's attempted coup will leave British tourists stranded in Turkey, but tanks were reported to be stationed outside Istanbul's Ataturk Airport and all flights were cancelled.
Since the beginning of 2016, Turkey has suffered six terrorist attacks, three having taken place in the country's capital, Ankara.
In the most recent attack, on Istanbul's Ataturk airport, the death toll alone was 41 with another 239 people injured.
The killings were the result of three suicide bombers and bore the hallmarks of an Islamic State attack.
More than 2.5 million Britons visit Turkey every year, but the country has seen a reduction in arrivals in 2016 as visitors heed travel advice and avoid the region.
The number of arrivals to Turkey decreased 34.7 per cent, year-on-year, for May, to 2.48 million, which was the biggest fall in 22 years.
One four-star hotel just outside Antalya, the Garden Resort Bergamot Hotel, last month said it should be 70 per cent full at this time of year, yet only 25 of its 233 rooms were taken.
Social media websites Twitter, Facebook and YouTube have reportedly all been blocked in the country.
British holidaymaker Gabriel Turner, 23, told how there had been large police and security presence throughout the day before last night's coup began.
The management consultant from north London told The Telegraph: 'Earlier today there were police everywhere. I thought that was normal but the two Turkish girls I was with told me it wasn't normal. We were walking around the centre of Istanbul, at the Grand Bazaar there were police at every entrance and exit with lots of guns.
'A police helicopter was flying very low at sunset, it was about 8pm. It looked like it was searching for something. Later on, at about 10.30 I was in Karakoy, a bar area in the city centre and everyone started looking at their phones. A man who owns the bar told us that the army are taking over everything.
'Then we walked down towards the a quieter area by the sea. While we were walking, my friend said the army had closed brides across the Bosphorus. We could see army helicopters in the sky.
'We went inside a cafe and everyone was on their phones looking worried, texting. Lots of people were running to catch a ferry - because the bridges were shutting and people wanted to get home. Then policemen came out of the ferries on their walkie talkies, looking very alert.'
The Foreign and Commonwealth Office currently advise against all travel to within 6 miles (10km) of the Turkish border with Syria.
It states that the threat from terrorism remains high and that 'terrorist groups and far left organisations continue to plan and carry out attacks'.
On its website, the FCO advises: 'You should take extra care in public places – particularly those visited by foreigners.
'Be vigilant, follow the advice of local security authorities, monitor media reports.
'Attacks are likely to target the Turkish state, civilians and demonstrations. Nevertheless, it's increasingly likely that some attacks will also target western interests and tourists from western countries.'
British Foreign Office Helplines
If you are in Ankara and urgently need help, call +90 312 455 3344.
If you are in Istanbul and you urgently need help, call +90 212 334 64 00.
If you're in the UK and concerned about a British national in Turkey, please call 020 7008 1500
By Patrick Lion
Editor’s note: This article has been edited from the source material
© Associated Newspapers Ltd.