Raphael Boukandoura, who works for various French publications including Ouest France and Courrier International, was arrested outside DEM's Istanbul headquarters in the Sancaktepe district, it said.

His arrest was also confirmed by Reporters Without Borders (RSF), who called for him to be freed without delay.

"We call for the immediate release of our colleague who did nothing but his legitimate duty to cover a protest," RSF's Turkey representative Erol Onderoglu told AFP.

"RSF is closely following his case and calls on the authorities to put an end to such arbitrary interference against media professionals," he said.

Ouest France echoed the call for him to be freed, demanding "the immediate release of Raphael Boukandoura who was covering the event" in a statement sent to AFP.

The police intervened after a DEM statement was read out calling for "an immediate halt to the attacks" and for the protection of civilians in northeastern Syria, Turkish news reports showed.

Syrian forces began an offensive nearly two weeks ago which pushed Kurdish-led SDF forces out of the northern city of Aleppo, and expanded over the weekend to push deep into territory that has been held by Kurdish forces for over a decade.

The move was hailed by Ankara as a legitimate "fight against terror" but triggered angry protests among Turkey's Kurds, who make up a fifth of the country's population of 86 million and who have been deeply unsettled by the violence.

It has also raised questions about the fate of Turkey's peace process with the Kurdish militant group PKK in a bid to draw a line under a four-decade insurgency that cost some 50,000 lives.