As Europe and the U.S. bear down with a raft of aggressive sanctions targeting Russian President Vladimir Putin, the super yacht he is believed to own has found safe harbor in a highly militarized port in Russian territorial waters. In new satellite imagery obtained by CBS News, the yacht can be seen docked in a port in Kaliningrad, near Russia's nuclear weapons operations.

Experts say Putin's luxury vessel has become a symbol not only of his vast hidden wealth, but also of how challenging that money has been to find.

"He's a KGB agent, so he's crafty. He knows how to hide when he needs to," said John Smith, former director of the Treasury Department's Office of Foreign Assets Control, which administers and enforces all foreign sanctions.

Data from MarineTraffic, a global intelligence group, shows Putin's alleged yacht, the Graceful, left Germany two weeks before the invasion of Ukraine.

Putin's government salary is said to be about $140,000, but that doesn't begin to explain the mansions, million-dollar watch collection and over-the-top yacht.

"It would be fair to say he's among the richest men in the world," Smith said.

Though he sells himself as a man of the people, his wealth is estimated to be more than $100 billion.

Putin's critics allege he also has a cliffside palace that includes an amphitheater and a personal tunnel to the beach that doubles as a security bunker.

"Of course, he doesn't acknowledge it as being his own," Smith said. "It doesn't fit with the public persona that he's trying to create to actually acknowledge it."

Putin relies on his oligarch friends to shield his fortune from sanctions, Smith said.

"So if he asked them to do something, they do it in terms of hiding assets, squirreling them in different parts of the globe, they will do what he needs," he said.

Those who have tried to expose Putin's fortune have done so at great personal risk.

Putin critic Boris Nemtsov was assassinated on a bridge in the shadow of the Kremlin in 2015. Sergei Magnitsky died in 2009 under questionable circumstances in prison after he exposed $230 million in fraud by Putin's friends. Putin publicly condemned Nemtsov's murder and claimed Magnitsky died of a heart attack.

His most recent No. 1 critic, Alexei Navalny, who helped expose Putin's lavish palace, emerged as a political rival and found himself repeatedly jailed. He nearly died after being poisoned two years ago, though Putin has denied responsibility for the poisoning.

"Putin's wealth is one of the most dangerous topics," said Russian journalist Roman Badanin, who spent two decades investigating Putin's financial web.

Badanin said Russian authorities sought to intimidate and silence his reporting team. Six months ago, he reached his breaking point.

"I fled the country. My apartment was searched twice. I have like three criminal charges against me back in Russia," he said.

In his State of the Union address, President Biden said the U.S. and its allies are waging economic war on Putin and Russian oligarchs.

"We are joining with our European allies to find and seize your yachts, your luxury apartments and your private jets," Biden said.

On Wednesday, the Justice Department announced the formation of a new task force that would target Russian oligarchs.

"Russia is not a transparent economy," Smith said. "The U.S. and our allies have decent information on some of [Putin's] assets, I think a lot will remain a mystery for a long time in the future."

The biggest financial hit for Putin would be sanctions on the energy sector, which Smith says the Russian president has used to build up his wealth for years. So far, Washington and the Europeans have been hesitant to do that.

Catherine Herridge is a senior investigative correspondent for CBS News covering national security and intelligence based in Washington, D.C.

More:

Satellite image shows super yacht linked to Putin out of reach of sanctions - CBS News