Turkish authorities released a lawyer for jailed Istanbul Mayor Ekrem Imamoglu, President Tayyip Erdogan's main political rival, after detaining him overnight, an attorney for the lawyer said on Friday.

Turkish authorities detained and deported BBC correspondent Mark Lowen​ and arrested other journalists amid the largest nationwide protests in a decade.

Tens of thousands of people gathered in Istanbul on Saturday to protest against the jailing of Mayor Ekrem Imamoglu, President Tayyip Erdogan's main rival, sustaining the largest demonstrations Turkey has seen in more than a decade.

Mahir Polat, deputy secretary-general of the İstanbul Metropolitan Municipality, was transferred back to prison after undergoing angioplasty at a hospital. Polat had been remanded in custody along with 50 others, including İstanbul Mayor Ekrem İmamoğlu.

Turkish authorities have detained 343 people during overnight protests in several cities against the detention of Istanbul Mayor Ekrem Imamoglu, the Interior Ministry said on Saturday.

More than 1,100 people, including some journalists, were detained in protests against Turkish President Erdogan after the arrest of his rival, Istanbul Mayor Ekrem Imamoglu.

The head of Turkey’s main opposition party has visited jailed Istanbul Mayor Ekrem Imamoglu after six nights of massive protests calling for his release.

Dozens of demonstrators marched through central Istanbul Thursday protesting the arrest of the city’s mayor. The demonstrations began last week following the arrest of Istanbul Mayor Ekrem Imamoglu, a key rival to President Recep Tayyip Erdogan.

Hundreds of thousands of protesters again congregated in Istanbul Saturday to how their support for the city's imprisoned mayor and demand his release.