Jan. 18 (UPI) -- A Russian court on Monday ordered opposition leader Alexei Navalny to be detained for one month after his return from Germany, where he was seeking treatment for poisoning, his lawyer said.
Moscow's Khimki Court ruled that Navalny must remain under arrest until Feb. 15, attorney Vadim Kobzev told Tass news agency.
Russian authorities arrested Navalny on Sunday upon his landing at Sheremetyevo airport. Kira Yarmysh, a spokeswoman for the opposition leader, said police gave no explanation for his arrest.
CNN reported he was held overnight Sunday at a police station in Khimki.
Russia's federal prison service released a statement on Thursday accusing Navalny -- who has been jailed multiple times for leading protests against Russian President Vladimir Putin -- of "malicious violations" of a suspended prison sentence from 2014 and pledging to arrest him.
Navalny became ill in August while on a flight from Siberia to Moscow and ultimately fell into a coma. Doctors later said he'd been poisoned with the Soviet-era nerve agent Novichok.
He later was transferred to Berlin's Charite hospital after the doctors at the Siberian hospital where he was first taken said they could find "no trace" of poison in his system, while hesitating to have him transferred.
Last month, Navalny said he was able to dupe a member of Russia's FSB spy agency into revealing that they were behind the poisoning but the Kremlin dismissed his claims.
Daniel Uria contributed to this report.