Russian investigators on Friday opened a criminal probe against a pregnant city councillor in Siberia who is one of the last allies of jailed opposition leader Alexei Navalny still in the country.

Russia's Investigative Committee said it launched criminal proceedings against Helga Pirogova over spreading false information about the army.

She is an independent member of the city council in Novosibirsk, Russia's third-largest city.

The 33-year-old has spoken up against Russia's military intervention in Ukraine and faces up to three years in prison if convicted.

Her supporters say Pirogova is in her fourth month of pregnancy

She was briefly detained on Thursday.

Investigators accused Pirogova of posting "false information" about the Russian army in mid-July, when she took to Twitter to comment on a report about the funerals of troops killed in Ukraine.

She said she wanted to "revive" the troops to punish them for their role in Moscow's offensive and then "let them go back to their graves."

Helga Pirogova (pictured in April) faces criminal proceedings
Helga Pirogova (pictured in April) faces criminal proceedings AFP / Rostislav NETISOV

She later deleted her tweet, calling it "too emotional."

Pirogova said she wanted to draw attention to the fact that people in Russian provinces were so poor that instead of mourning their dead they admired the funeral arrangements made by officials.

"You can invite half the village!" she said in a Facebook post this week.

In March, Pirogova caused an uproar when she turned up at a council meeting wearing a blue shirt and a crown of yellow flowers -- the colours of the Ukrainian flag.

When Pirogova was elected in 2020, she was part of a coalition of Navalny's allies and independent candidates who were allowed to run for office in exceptional circumstances.

Putin's decision to send troops to Ukraine on February 24 accelerated an already ruthless crackdown on dissent.

Nearly all key opposition figures are now either in exile or in jail, and virtually any criticism of Moscow's offensive in Ukraine has been outlawed.

"I do not support any conflict and what is happening is an immense tragedy for everyone," Pirogova, a teacher by training, told AFP in an interview this March.