By Anton Zverev and Andrew Osborn
MOSCOW (Reuters) - A Russian judge remanded Kremlin critic Alexei Navalny in pre-trial detention for 30 days on Monday for violating the terms of a suspended jail sentence, ignoring calls from Western countries to free the opposition politician immediately.
The ruling, a day after police detained him at the airport when he returned to Russia for the first time since being poisoned by a military-grade nerve agent last August, could be the prelude to him being jailed for years.
Moscow's prison service has applied to convert a suspended three-and-a-half year embezzlement sentence in the same case, which he says was trumped up, into real jail time early next month.
He faces three other separate criminal cases too.
The United Nations and Western countries told Moscow before the ruling to let Navalny go, and some countries have called for new sanctions after earlier penalties from the EU over his poisoning. Moscow told them to mind their own business.
Navalny, in a video released on Twitter after the ruling, urged Russians to protest.
"Don't be afraid, take to the streets. Don't go out for me, go out for yourself and your future," Navalny said.
Leonid Volkov, a Navalny ally, wrote on Twitter that supporters would hold rallies nationwide on Saturday.
Navalny, 44, called his treatment illegal under Russian law and accused President Vladimir Putin of throwing the criminal code out of the window in fear.
The Kremlin did not respond, but has previously said Navalny must face justice if he has done anything wrong.
About 200 Navalny supporters had gathered outside the police station in freezing temperatures and demanded he be set free, a Reuters witness said.
Four masked police officers detained Navalny at passport control on Sunday evening as he returned to Russia after being treated in Germany for what German military tests showed was poisoning by a Novichok nerve agent, a version of events the Kremlin rejects.
The rouble weakened as investors weighed the risk of new sanctions against Moscow.
CALLS FOR SANCTIONS
Lithuania, Latvia and Estonia said they wanted European Union foreign ministers to discuss further sanctions against Russia on Monday for detaining Navalny, whose foundation specialises in investigations into alleged official corruption.
Some of the foundation's targets have taken legal action and some critics have upbraided Navalny in the past for espousing overly nationalist views, something he rejects.
A possible target of any new penalties would be Nord Stream 2, a $11.6 billion project to build a natural gas pipeline from Russia to Germany. Germany has supported the project, saying it is a commercial venture, and government spokesman Steffen Seibert said on Monday that had not changed.
The foreign ministers of Germany, Britain, France and Italy had earlier called for Navalny's release and Czech Foreign Minister Tomas Petricek had said he wanted the EU to discuss possible sanctions.
The U.N. human rights office called for Navalny's immediate release and demanded due process in line with the rule of law. Jake Sullivan, one of U.S. President-elect Joe Biden's top aides, and U.S. Secretary of State Mike Pompeo have criticised the arrest.
The Russian Foreign Ministry brushed off the criticism.
"Respect international law, do not encroach on national legislation of sovereign states and address problems in your own country," Foreign Ministry spokeswoman Maria Zakharova wrote on Facebook (NASDAQ:FB).
Foreign Minister Sergei Lavrov said Western countries' expressions of outrage were designed to distract their citizens' attention from domestic problems and that Moscow was unfazed by potential damage to its image.
"We should probably think about our image, but we're not young ladies going to a ball," Lavrov told reporters.
Moscow residents interviewed by Reuters TV were divided on Navalny's detention.
"He probably did the right thing and acted like a real man (by returning)," said one Muscovite, Yuri Elizarov. "But from a political viewpoint he didn't, because nothing is probably going to change here in the coming years."