Police detain a woman during a protest against the jailing of Alexei Navalny in the Siberian city of Omsk, Russia. File

Russia's Foreign Ministry said Friday it was expelling diplomats from Sweden, Poland and Germany for attending a rally in support of opposition leader Alexei Navalny.

The announcement came as the European Union’s top diplomat told Russia’s foreign minister that the treatment of Navalny represents "a low point” in the relations between Brussels and Moscow.

EU foreign policy chief Josep Borrell "strongly condemned" Moscow's expulsion of three European diplomats when he was informed of it during a meeting with Russian Foreign Minister Sergei Lavrov on Friday, a spokesman said.

"During the meeting with FM Lavrov, HRVP Borrell learned that three European diplomats are going to be expelled from Russia," EU spokesman Peter Stano said, referring to Borrell's position as High Representative of the European Union.

"The HRVP strongly condemned this decision and rejected the allegations that they conducted activities incompatible with their status as foreign diplomats. The decision should be reconsidered."

The ministry said diplomats from Sweden and Poland in St. Petersburg and from Germany in Moscow took part in what it called "unlawful” rallies on Jan.23. Tens of thousands of people across Russia took to the streets that day to protest the arrest of Navalny, the Kremlin's most prominent critic.

The diplomats were declared "persona non grata” and were required to leave Russia "shortly,” a ministry statement said.

EU foreign affairs chief Josep Borrell, who met earlier Friday with Russian Foreign Minister Sergey Lavrov, said before the session that "our relations are under a severe strain, and the Navalny case is a low point in our relations.”

Navalny, 44, an anti-corruption investigator and Russian President Vladimir Putin’s most prominent critic, was arrested Jan.17 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.

On Tuesday, a Moscow court ruled that while in Germany, 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. The ruling prompted international outrage.

After his meeting with Lavrov, Borell said he had relayed his concerns over Navalny’s jailing and the arrests of thousands of people who demonstrated in his support.

The EU official said he also communicated the bloc's support for Navalny's release and for an investigation of the August poisoning.

Lavrov, in turn, 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.