Police have detained more than 1,100 people, officials said, since the arrest of President Recep Tayyip Erdogan's main rival triggered some of Turkey's worst unrest in years.

The demonstrations began in Istanbul after Ekrem Imamoglu's arrest last week and have since spread to more than 55 of Turkey's 81 provinces, sparking clashes with riot police and drawing international condemnation.

The popular 53-year-old has been widely seen as the only politician who could defeat Turkey's longtime leader Erdogan at the ballot box. In just four days he went from being the mayor of Istanbul to being arrested, interrogated, jailed and stripped of the mayorship as a result of a graft and terror probe.

On Sunday, he was overwhelmingly voted in as the main opposition CHP's candidate for the 2028 presidential run, with the ballot - that was opened beyond the party's 1.7 million members - attracting 15 million votes. Observers said it was the looming primary that triggered the move against Imamoglu, the main political rival of Erdogan who has dominated Turkey's politics since 2003.

His jailing drew a sharp condemnation from Germany, which called it "totally unacceptable."

Police have detained more than 1,133 people over "illegal activities" since the protests began last Wednesday, Interior Minister Ali Yerlikaya said.

As he was being shipped off to Silivri prison on the megacity's western outskirts, Imamoglu had denounced the judicial moves against him as a political "execution without trial."

In a later message from prison, he sounded a defiant tone.

"I wear a white shirt that you cannot stain. I have a strong arm that you cannot twist. I won't budge an inch. I will win this war," he said in the message passed through his lawyers.

AGENce FRANCE-Presse

A demonstrator in Istanbul. REUTERS

Turkey detains 1,100 after Istanbul mayor's arrest