Turkish authorities detained prominent independent journalist Fatih Altayli on Saturday over social media comments allegedly threatening President Tayyip Erdogan, the Istanbul prosecutor’s office said.

Altayli, who has more than 1.51 million subscribers on his YouTube channel, posted a video on Friday referencing an unnamed poll showing 70% of Turks opposed Erdogan ruling for life, saying this would “never be allowed” by the Turkish people.

Altayli also referenced past Ottoman rulers in his comments, saying people had “drowned”, “killed”, or “assassinated them in the past.” His comments drew backlash from an Erdogan aide, Oktay Saral, who said on X that Altayli’s “water was boiling”.

In a statement, the Istanbul prosecutor’s office said the comments from Altayli “contained threats” against Erdogan, and said an investigation has been launched against him. Legal representation for Altayli could not immediately be reached for comment.

Altayli’s detention comes amid a series of detentions of opposition figures in recent months, including the arrest in March of Istanbul Mayor Ekrem Imamoglu who is Erdogan’s main political rival.

The main opposition CHP says the detentions and arrests of its members, along with other opposition members and journalists or media personalities, is a politicised move by the government to muzzle dissent and eliminate electoral challenges to Erdogan.

The government denies these claims, saying the judiciary and Turkey’s courts are independent.

Turkish authorities have in the past carried out widespread detentions and arrests against opposition politicians, namely pro-Kurdish local authorities. More than 150 people jailed so far over what Erdogan’s government says is a ring of corruption that the CHP denies.