“If I die under mysterious circumstances, it’s been nice knowin ya,” the billionaire Tesla cofounder told his 91.6 million Twitter followers on Sunday night, after claiming he’d been threatened by a top Russian official over SpaceX’s use of its Starlink satellites to provide internet in Ukraine.

Starlink uses satellites to provide high-speed broadband internet around the world.

Since Russia invaded the country on February 24, there have been reports of connectivity problems across Ukraine, prompting Musk to send in Starlink to help.

Starlink now has around 150,000 active users per day in Ukraine, according to the country’s Deputy Prime Minister, Mykhailo Fedorov.

But Dmitry Rogozin, head of Russian state space agency Roscosmos and the country’s former deputy prime minister, hasn’t taken kindly to Starlink’s presence in Ukraine.

“Elon Musk is involved in supplying the fascist forces in Ukraine with military communication equipment,” he said in a post on the Telegram messenger app on Sunday.

“And for this, Elon, you will be held accountable like an adult—no matter how much [you] play the fool.”

Rogozin’s words on Sunday were accompanied by a short clip of Musk jokingly posing in front of photographers as he arrived at the Met Gala in New York with his mother last week.

Musk’s mom, Maye Musk, weighed in on her son’s predicament on Monday, telling him in a tweet that she didn’t approve of his joke about dying a suspicious death.

“I will do my best to stay alive,” Musk replied.  

On Monday, Rogozin responded to Musk’s cryptic tweets about a mysterious death via his own social media accounts.

“Nobody needs you. Stop fooling around,” he said, according to a translation. “Today my country celebrates a great day—Victory Day over fascism.”

He added: “After what you did by supplying the means of communication to the Ukrainian Nazis, unfortunately I cannot congratulate you on this holiday. Think, Elon, which side are you on?”

The Kremlin’s false claims that Ukraine is being governed by a fascist or Nazi regime have been widely criticized in the West as an attempt to justify Moscow’s invasion.

The Kremlin has continuously made unsubstantiated claims that it is seeking to “denazify” Ukraine with its so-called “special operation” in the country.

But Moscow’s claims about Nazism have been rejected by Western governments.

Back in March, U.S. President Joe Biden slammed his Russian counterpart Vladimir Putin’s claims as “obscene.”

On May 9, Russia celebrates Victory Day to commemorate the end of World War II. The day is marked with military parades that are traditionally watched by political leaders in Moscow.