A Moscow court has extended the pretrial detention of prominent Russian opposition activist Vladimir Kara-Murza, who was arrested for allegedly spreading false information about the Russian Army.

The Basmanny district court on June 8 ruled that the 40-year-old Kremlin critic will remain in pretrial detention at least until August 12.

Russia's Investigative Committee is conducting a probe into allegations that Kara-Murza distributed false information about the army while speaking to lawmakers in the U.S. state of Arizona.

Kara-Murza has rejected the charge, calling it politically motivated.

Kara-Murza was arrested outside his home in Moscow on April 11 and sentenced the next day to 15 days in jail on a charge of disobeying the police. He was later charged with spreading false information about the Russian Army.

His arrest came amid a mounting crackdown by Russian authorities on opposition figures and any dissent to the ongoing war in Ukraine that started on February 24.

In early March, President Vladimir Putin signed a law that calls for lengthy prison terms for distributing "deliberately false information" about Russian military operations.

The law envisages sentences of up to 10 years in prison for individuals convicted of an offense, while the penalty for the distribution of "deliberately false information" about the Russian Army that leads to "serious consequences" is 15 years in prison.

It also makes it illegal "to make calls against the use of Russian troops to protect the interests of Russia" or "for discrediting such use" with a penalty possible of up to three years in prison. The same provision applies to calls for sanctions against Russia.

A close associate of slain opposition leader Boris Nemtsov, Kara-Murza is best known for falling gravely ill on two separate occasions in Moscow -- in 2015 and 2017-- with symptoms consistent with poisoning.

Tissue samples smuggled out of Russia by his relatives were turned over to the FBI, which investigated his case as one of "intentional poisoning."

U.S. government laboratories also conducted extensive tests on the samples, but documents released by the Justice Department suggest they were unable to reach a conclusive finding.

With reporting by TASS and Interfax