ODESA, Ukraine -- Security has been beefed up in Ukraine's Black Sea port city of Odesa as ceremonies are under way to commemorate 48 people killed in a 2014 clash between pro-Ukrainian and pro-Russian demonstrators.
More than 1,000 police and security officers were deployed on May 2 near Kulikovo field and the Trade Unions building, where the deadly clashes took place four years ago.
The Odesa regional police department said that people can reach the area only after passing through metal detectors.
The Security Service of Ukraine (SBU) said that communist and Nazi symbols are prohibited at the commemoration events.
Since 2014, pro-Russian and pro-Ukrainian activists have come to the site on May 2 to commemorate the victims. Fighting has broken out at times.
The regional police said that 2,500 police and National Guard troops were patrolling the streets of Odesa.
Four years ago, on the wake of Russia's annexation of Ukraine's Crimea and supporting pro-Russian separatists in Ukraine’s eastern regions of Donetsk and Luhansk, pro-Russian activists and their opponents marched in Odesa.
The marches led to clashes between the opposing sides and gunfire that killed several people in the city center.
Then the clashes moved to the Kulikovo field and ended with a fire at a trade union building where supporters of autonomy for Ukraine's east took shelter from government backers.
It is unclear how the fire started. Government supporters threw firebombs at the building, but official accounts say those inside the building may have caused the fire by throwing firebombs at their opponents from the roof.
Forty-two people died in the building.