BBCBBC correspondent Mark Lowen has been deported from Turkey after being arrested in Istanbul on Wednesday, the BBC has said.
Lowen had been in Turkey for several days to report on the ongoing protests that were sparked by the Istanbul Mayor Ekrem Imamoglu's arrest last week.
Imamoglu - who is being held in jail on corruption charges he denies - is seen as President Recep Tayyip Erdogan's main political rival.
He has been selected by his party as presidential candidate in the 2028 election.
In a statement issued on Thursday, the BBC said: "This morning (27 March) the Turkish authorities deported BBC News correspondent Mark Lowen from Istanbul, having taken him from his hotel the previous day and detained him for 17 hours.
On Thursday morning, he was presented with a written notice that he was being deported for 'being a threat to public order'."
Mark Lowen said: "To be detained and deported from the country where I previously lived for five years and for which I have such affection has been extremely distressing. Press freedom and impartial reporting are fundamental to any democracy."
The BBC's CEO of News Deborah Turness added: "This is an extremely troubling incident and we will be making representations to the Turkish authorities.
"Mark is a very experienced correspondent with a deep knowledge of Turkey and no journalist should face this kind of treatment simply for doing their job. We will continue to report impartially and fairly on events in Turkey."
Thousands of people across Turkey have turned out for protests which have so far seen more than 1,400 people detained.
The protesters say Imamoglu's arrest is politically motivated, but the justice ministry insists on its judicial independence.
President Erdogan has labelled the demonstrations "evil" and blamed the opposition for "disturbing the peace".
Several journalists have also been arrested, including a photojournalist from French news agency Agence France Presse and several Turkish reporters. Many were reportedly released on Thursday morning.
Nightly protests have stopped but Turkey's main opposition party, the Republican People's Party (CHP), is planning a rally in Istanbul on Saturday.
