ISTANBUL, May 8, 2025 (BSS/AFP) - Turkish authorities on Thursday blocked access to the social media account of Istanbul's jailed opposition mayor Ekrem Imamoglu, who has nearly 10 million followers on X.

Imamoglu, who was detained on March 19 on corruption charges he strongly denies, is seen as the biggest rival to longtime leader President Recep Tayyip Erdogan. The arrest could stop Imamoglu taking part in presidential elections scheduled for 2028.

It was not possible to access to his X account on Thursday morning. A message read: "Account Withheld -- @ekrem_imamoglu has been withheld in TR (Turkey) in response to a legal demand."

A spokesperson for the Istanbul municipality also confirmed the access was blocked, without giving further details.

Watchdog group EngelliWeb, which reports Internet censorship and blocked web sites in Turkey, said on X that access to Imamoglu's account had been blocked on national security grounds.

The account "has been blocked under Article 8/A of Law No. 5651, on the grounds of protecting national security and public order, and has been made invisible in Turkey by X", it said.

On his last message on X, Imamoglu, who is jailed in Silivri prison on the outskirts of Istanbul, urged his supporters to join a protest rally held Wednesday, which was called by his CHP party.

Tens of thousands of people took part in the Istanbul rally, one of the biggest in recent weeks.

In the days after Imamoglu's arrest, tens of thousands of people took part in near-daily protests. But numbers had dwindled in recent weeks.

Wednesday's protest was held outside Istanbul University, which had stripped Imamoglu of his degree the day before his arrest.