Police in Turkey have detained the chief editor of an opposition English-language newspaper for posting tweets critical of President Recep Tayyip Erdogan.

Bulent Kenes, editor-in-chief of Today's Zaman, was taken away from the newspaper's headquarters in Istanbul on Friday as supporters chanted: "Free media cannot be silenced!" The detention was televised live.

A court issued a warrant for his arrest for tweets that a Turkish prosecutor says insult Erdogan. Kenes, who received a suspended sentence earlier this year for insulting the president, denies the accusation, insisting he is exercising his right to free speech.

Dozens of people have been prosecuted under a previously seldom-used law that bars insults to the president. Free speech advocates say the law is being used aggressively to muffle dissent.