Belgrade, Serbia - Renowned Russian chef Alexei Zimin, a vocal critic of Russia's invasion of Ukraine, was found dead in a Belgrade hotel room on Tuesday, sparking concerns of foul play. He was 52.

Zimin, who owned the London-based restaurant "Zima," was in the Serbian capital to promote his new book, "Anglomania." Belgrade prosecutors have stated that the room was locked from the inside and there were no immediate signs of foul play, but an autopsy has been ordered. The exact cause of death has not been disclosed.

The untimely demise of Zimin in Serbia, a country with traditionally close ties to Russia, has raised suspicions, particularly given the history of unexplained deaths among Russian dissidents abroad.

Born in 1971 in Russia, Zimin operated several restaurants in Moscow before relocating to the UK in 2014 following his public condemnation of Russia's annexation of Crimea. After Russia's full-scale invasion of Ukraine in February 2022, Zimin continued to voice his opposition on social media, leading to the cancellation of his appearances on Russian TV cooking shows.

In a May 2022 interview with the BBC, Zimin revealed that his London restaurant had faced a wave of cancellations and threats following the invasion.

The Instagram account of Zimin's London restaurant, "Zima," posted a tribute, describing him as "not only a colleague but also a friend, a close companion with whom we shared many experiences."

The circumstances surrounding Zimin's death have prompted speculation and calls for a thorough investigation.