A prominent Russian politician who supported President Vladimir Putin's invasion of Ukraine and the annexation of Russian-occupied eastern Ukrainian territories recently died under questionable circumstances.

In what was dubbed a "terrible tragedy" by some, Russian Sen. Vladimir Lebedev died "suddenly" at the age of 61, according to the U.K. Mirror.

The air of mystery surrounding Lebedev's death follows in short order the sudden and unexpected death of a former close business associate, Vladimir Nekrasov, 66, and the recent curious deaths of other prominent figures within Russia's banking and energy production sectors.

"Shocked" regional governor calls senator's death a "terrible tragedy"

A Russian media outlet reported that Sen. Lebedev, who was born in 1962 and served as a member of Russia's Federation Council and First Deputy Chairman of the Council's Committee on Agricultural and Food Policy and Environmental Management, passed away unexpectedly on Thursday.

That news was first announced by Gleb Nitikin, the regional governor of Nizhny Novgorod, which Lebedev represented in the Federation Council, in a social media post.

"Professional. Partial. Positive. Creator ... Just on a personal note -- a very good person!" Nitikin wrote. "I have no words ... All of us who knew him well and were friends with him are shocked ... a terrible tragedy."

The governor went on to express his condolences to the family and friends who were in mourning over the loss of the senator.

Latest in growing list of suspicious or unexplained deaths

The Mirror noted that initial reports said that Lebedev had died from a "heart attack" but few additional details were given.

It was further observed that one of the senator's close former associates, Nekrasov, with whom he previously worked together for Russian energy giant Lukoil, had similarly died "suddenly" from "acute heart failure" less than a month earlier.

Radar Online reported that over the past two years, or since the Russian invasion of Ukraine was first launched in early 2022, more than 40 prominent Russian figures have "died under sudden and mysterious circumstances."

That includes wealthy oligarchs, politicians, and high-ranking members of the military, typically after having spoken critically of Russia's war effort in Ukraine or of President Putin himself -- though all evidence suggests that Lebedev fully supported Russia's military actions in Ukraine and the annexation of certain breakaway portions of Ukrainian territory that had been fought over for nearly a decade prior to the current expanded conflict.

Sanctioned by the U.S. and other Western nations

Indeed, both the Mirror and Radar Online reported that Sen. Lebedev had been economically sanctioned by multiple Western governments -- including the European Union, the United Kingdom, and the United States, among others -- in response to his expressed support for President Putin's military actions against Ukraine.

In fact, a September 2022 press release from the U.S. Treasury Department, as part of a broad and massive imposition of sanctions against hundreds of Russian individuals and entities, specifically cited the Russian Federation Council's unanimous votes in support of Russia's initial invasion of Ukraine, passage of a law that criminalized criticism of the Russian government and war effort, and its support for the "sham referenda and attempt to annex sovereign Ukrainian territory" as the reasons behind adding all members, including Lebedev, to the Office of Foreign Assets Control's Specially Designated Nationals List.

"We will not stand by as Putin fraudulently attempts to annex parts of Ukraine. The Treasury Department and U.S. government are taking sweeping action today to further weaken Russia’s already degraded military industrial complex and undermine its ability to wage its illegal war," Treasury Sec. Janet Yellen said at the time. "We are also targeting key leaders in Russia’s financial architecture as part of our aggressive and coordinated effort to hold Putin and his enablers accountable for his unprovoked invasion, and limit their ability to prop up their economy. The Treasury Department, U.S. government, and our allies will not hesitate to take swift and severe actions against individuals and companies inside and outside of Russia who are complicit in this war and these sham referendums."