KYIV, Ukraine (AP) — Ukraine's president asked the leader of Belarus on Wednesday to hand over some Russian security contractors detained on terrorism charges who also are accused of fighting alongside Russia-backed separatists in eastern Ukraine.

“I hope that all those suspected in terrorist activities on Ukrainian territory will be handed over to us for prosecution in accordance with the existing international norms,” according to a readout of a phone call between President Volodymyr Zelenskiy and Belarusian President Alexander Lukashenko released by the Ukrainian president's office.

Belarusian authorities detained 33 contractors for a private Russian security firm last week and accused them of of plotting terror attacks in advance of the presidential election in Belarus this weekend.

Officials in Kyiv said Friday they would ask Belarus to transfer 28 of the detainees, nine of whom also have Ukrainian citizenship. In Ukraine, they would face a criminal probe on the charges of involvement in a terrorist group for fighting on the side of the rebels in eastern Ukraine, the Prosecutor General's office said.

The government in Minsk claimed the detained contractors worked for the Wagner company — a private military firm linked to Yevgeny Prigozhin, a Russian businessman who was indicted in the United States for meddling in the 2016 U.S. presidential election.

Wagner has allegedly deployed hundreds of military contractors to eastern Ukraine, Syria and Libya.

The allegations against the Russians represent an unprecedented escalation of tensions between Russia and neighboring Belarus, traditionally close allies, as Lukashenko seeks a sixth term in Sunday's election amid mass opposition rallies.