Russian opposition leader Alexei Navalny was sentenced to 20 days in jail for organising an anti-Kremlin protest in a new court ruling Monday, the day he was freed after spending a month behind bars.
The authorities have turned up the heat on Vladimir Putin's top foe after the Russian president's popularity ratings have taken a beating and the Kremlin suffered a string of rare electoral defeats this month.
"Twenty days," Navalny's spokeswoman Kira Yarmysh said on Twitter after a Moscow district court issued the ruling late Monday.
The 42-year-old anti-corruption campaigner will have spent a total of 50 days in prison for organising two opposition protests.
Navalny's allies fear that the two consecutive administrative cases mean the authorities may be getting ready to open a criminal probe against him.
In that case he could face a lengthy prison term.
Navalny was detained early Monday immediately upon his release from jail after serving a 30-day sentence for organising an opposition rally in January.
He spent some eight hours in a holding cell ahead of the trial and looked tired and gaunt in court.
The new ruling is related to Navalny's call to Russians to take to the streets on September 9 in protest against a controversial Kremlin-backed plan to raise the state pension age.
Navalny timed the protest to coincide with a nationwide election when Russians voted to elect a Moscow mayor and regional governors, among others.
Navalny was jailed ahead of the protests, when thousands rallied across Russia and more than a thousand people were detained, according to an independent monitor.
The authorities have claimed that because of Navalny, two police officers were hurt during the September rallies, Yarmysh said.
- 'Prisoner of conscience' -
Ahead of the ruling, Amnesty International urged the Russian authorities to release Navalny.
"He is a prisoner of conscience who has not committed any crime," Natalia Zviagina, director of Amnesty International in Russia, said in a statement.
"They have to take it out on someone because of all their defeats and failures of the last weeks," Leonid Volkov, a key ally of Navalny, said on Twitter.
Public anger over the pension age hike and falling living standards as a result of tough Western sanctions over Ukraine and other crises has led to rare election reverses for the Kremlin.
This month the Kremlin suffered a string of setbacks as candidates of the ruling United Russia party failed to secure victories in four regions, including in Primorsky Krai and Khabarovsk in the far east, and south Siberia's Khakasia.
On Sunday, a second round of gubernatorial elections was held in two regions -- Vladimir, 190 kilometres (120 miles) northeast of Moscow, and Khabarovsk -- but candidates of the United Russia ruling party were defeated by nationalists from the LDPR party.
In an unprecedented move, the second round run-off in Primorsky Krai was cancelled last week following protests over vote-rigging in favour of the Moscow-backed candidate and a re-run is expected to take place in three months.
Khakasia is yet to hold a run-off vote.
- 'Panicking and taking revenge' -
The plan to raise the state pension age has seen Putin's approval rating take a major hit.
Lyubov Sobol, a Navalny associate, said he was detained again "because the authorities are now weaker than ever".
"The overwhelming majority of people are against raising the retirement age and United Russia was defeated in gubernatorial elections in key regions," she wrote on Twitter.
"They are scared, panicking and taking revenge."
Navalny shot to prominence as an organiser of huge anti-Putin rallies that shook Russia in 2011 and 2012 following claims of vote-rigging in parliamentary polls.
His anti-corruption rhetoric is especially popular with younger people who follow his online channels and blogs.
He was barred from running against Putin in a presidential election in March and served a month in prison in June after organising demonstrations ahead of Putin's swearing-in ceremony for a fourth Kremlin term in May.
The Yale-educated lawyer has faced a string of charges since he became the leading opposition figure in Russia.
Navalny has been arrested nine times and has spent a total of 172 days in jail, his spokeswoman said.