Russian nuclear attack submarines conducted a mission where they approached U.S. military bases with the intent of staying undetected, a Russian military official told Russian state-owned media.

“This mission has been accomplished, the submarines showed up in the set location in the ocean and returned to base,” Russian navy submarine officer Sergey Starshinov told RT, a Russian state-owned media outlet.

Starshinov claimed Russian submarines came “close enough” to American shores and were “undetected,” but did not infringe on U.S. maritime borders.

The claims from Russian officials have not been verified, and Russian media has a reputation for pushing Russian President Vladimir Putin’s agenda. Russian media allegedly will publish a television series on the missions.

The Pentagon did not immediately respond to a request for comment.

Earlier this month, Putin announced that Russia had created nuclear weapons systems that could circumvent Western missile defenses. He claimed the weapons were needed because missile defense interceptors had expanded in the U.S., Europe, and Southeast Asia.

He also showed a video that appeared to display images of nuclear missiles aimed for the U.S.

In response to Putin’s announcement, State Department spokeswoman Heather Nauert said that U.S. military capabilities “remain unmatched.”

“U.S. defense capabilities are and will remain second to none,” Nauert told reporters earlier this month. “[W]e’re moving forward to modernize our nuclear arsenal and ensure that our capabilities remain unmatched.”

