Lukoil, Russia's second-largest oil company, said Tuesday its chairman had died suddenly, at the age of 66.

"It is with deep regret that we announce the sudden passing of Vladimir Ivanovich Nekrasov," the company said in a statement posted to its website. "According to the preliminary conclusion of doctors, death occurred as a result of acute heart failure."

Nekrasov had worked for almost 50 years in the oil and gas industry. He had also held positions as Lukoil's first vice president and an adviser to the company's president, Lukoil said.

Reuters reported that the company declined further comment about Nekrasov's death.

His immediate predecessor, Ravil Maganov, died just over a year ago after falling out of a hospital window in Moscow, according to Russian state media.

Maganov's death was confirmed by Lukoil in September 2022 in a statement that said he "passed away following a severe illness" but made no mention of a fall.

Lukoil, which produces more than 2% of the world's crude oil and employs more than 100,000 people, made headlines in March 2022 when it became one of only a few Russian companies to take a public stand on Moscow's full-scale invasion of Ukraine.

In a statement to shareholders, customers and staff, Lukoil's board of directors called "for the soonest termination of the armed conflict" in Ukraine.

"We express our sincere empathy for all victims, who are affected by this tragedy," it said. "We strongly support a lasting ceasefire and a settlement of problems through serious negotiations and diplomacy."

At least eight prominent Russian businessmen died suddenly in the months following the invasion.