MOSCOW (AP) — The European Union’s top diplomat told Russia's foreign minister Friday that the treatment of Russian opposition leader Alexei Navalny represents “a low point” in the relations between Brussels and Moscow.

EU foreign affairs chief Josep Borrell met with Russian Foreign Minister Sergey Lavrov several days after Navalny was ordered to serve nearly three years in prison, a ruling that elicited international outrage.

“Certainly, our relations are under a severe strain, and the Navalny case is a low point in our relations,” Borrell said ahead of his talks with Lavrov in Moscow.

Navalny, 44, an anti-corruption investigator and Russian President Vladimir Putin’s most prominent critic, was arrested last month upon returning from Germany, where he spent five months recovering from a nerve-agent poisoning that he blames on the Kremlin. Russian authorities have rejected the accusation.

After the meeting, Borell said he had relayed to Lavrov his concerns over Navalny’s jailing and the arrests of thousands of people who demonstrated on his behalf. The EU official said he also communicated the bloc's support for Navalny's release and for an investigation of the August poisoning,

The Russian foreign minister, in turn, once again accused European officials of refusing to share evidence of the poisoning. The Kremlin has said it won’t listen to Western criticism of Navalny’s sentencing and police action against his supporters.

Navalny's Jan. 17 arrest triggered massive protests across Russia, with tens of thousands of people rallying in the streets to demand his release. Many protesters chanted slogans against Putin in the largest show of discontent in years. Thousands of protesters have been detained.

A Moscow court on Tuesday found that Navalny violated probation terms of his suspended sentence from a 2014 money-laundering conviction, and ordered him to serve two years and eight months in prison.

Navalny on Friday appeared in another court on a charge of slandering a World War II veteran featured in a pro-Kremlin video.

A criminal probe of the politician was opened after he slammed people featured in a video promoting constitutional amendments last year that allowed an extension to President Vladimir Putin’s rule. Navalny called the people in the video “corrupt stooges,” “people without conscience” and “traitors.”

Russian authorities maintained that Navalny’s comments “denigrate (the) honor and dignity” of a World War II veteran featured in the video. If convicted, Navalny faces a fine or community service.

He has denied the charge and refused to plead guilty on Friday. He called the trial a “PR process" aimed at disparaging him.

"The Kremlin needs headlines (saying that) Navalny slandered a veteran,” he said.

The 94-year-old veteran, Ignat Artemenko, took part in the hearing via teleconference. He said he was distressed by Navalny's comments and demanded a public apology. The judge ordered a recess several hours after the hearing started, citing Artemenko's health.