Security fears force Britain's Turkey embassy to remain closed
The embassy, like most foreign missions in Turkey, had been closed for consular services throughout the Islamic Eid al-Adha holiday which began on Monday.
It had been due to reopen on Friday, with the holiday officially over.
"The British Embassy Ankara will be closed to the public on Friday 16 September for security reasons," it said in a statement on Thursday, without giving further details.
Turkey has this year been hit by a string of attacks blamed on the IS group and Kurdish militants. Several foreign missions have closed down on occasion due to security alerts.
Separately, the German embassy in Ankara said German missions in Turkey would "provide limited services until Friday" and "remain closed for any meetings", without giving further details.
Germany's mass-circulation daily Bild had said that diplomatic missions as well as German schools in Turkey were closed due to fears of an attack.