Dozens of protesters gathered in Istanbul to celebrate the May 1 holiday were detained today by the police, according to journalists from the AFP news agency.

The first clashes took place when protesters tried to break through police barriers to reach Taksim Square, which is a landmark for demonstrations in Istanbul.

The police surrounded Istanbul, notably blocking the center of Turkey's main city.

More than 42,000 police officers have been deployed in the city, Interior Minister Ali Yerlikaya warned on Tuesday, denouncing that "terrorist organizations (want) to turn May 1 into a field for action and propaganda".

From the banks of the Bosphorus to the historic Sultanhamet peninsula and Topkapi Palace, metal barriers are blocking people's passage. Public transport, including ferries, is at a standstill, causing inconvenience to tourists visiting the city.

Since this morning, as protesters gathered in the Besiktas neighborhood to celebrate May 1, clashes with the police broke out and several dozen people were taken into custody in police vans.

Another demonstration that was due to take place in front of the Istanbul municipality building, called by the city's mayor, Ekrem Imamoglu, and his party (CHP - the main opposition party in the Turkish parliament), was also prevented from going ahead.

Speaking alongside Ekrem Imamoglu, who was re-elected on March 31, CHP chairman Özgür Özel promised "not to give up".

"We will continue our efforts until Taksim Square is free," he said.

"(Taksim Square) belongs to the workers," Özel declared, then addressed the police: "these workers are not your enemies. Our only wish is for this day to be celebrated as a holiday".

Meetings are no longer allowed in Taksim Square, which has become the epicenter of the challenge to Turkish President Recep Tayyip Erdogan's power since the wave of protests that shook the country in 2013. But trade union and political organizations regularly call on their members to converge on the square.

On Tuesday night, Erdogan denounced "terrorist organizations that want to turn May 1 into a propaganda tool" and warned trade unions and political parties against "any action that would harm the atmosphere of May 1".