MOSCOW: A Russian court on Thursday upheld a decision to detain top opposition leader Alexei Navalny for 30 days after he returned to Moscow this month following a near-fatal poisoning.

Judge Musa Musayev of the Moscow Regional Court said a previous ruling by the Khimki City Court should "remain unchanged", an AFP journalist reported.

During the hearing, Navalny during the hearing slammed what he described as the "lawlessness" of the process.

"This is blatant lawlessness to intimidate myself and other people," Navalny told the court by video link.

Police detained President Vladimir Putin's top domestic critic in a Moscow airport after he returned to Russia on January 17 from Germany.

He had been recovering there from a near-fatal poisoning with the Novichok nerve agent in an attack he blamed on Russian security services and Putin.

The 44-year-old anti-graft campaigner is accused of violating probationary terms of his 2014 suspended sentence on fraud charges by not appearing at Russia's prison service for checks twice a month.

A makeshift court at a police station last week ordered Navalny placed in custody until February 15.

He was then moved to Moscow's Matrosskaya Tishina, a high-security detention centre.

Thursday's ruling came after Navalny's team called for fresh demonstrations on Sunday against Putin's 20-year rule.