The FBI and Justice Department obtained a secret warrant last summer to monitor the communications of an adviser to then-presidential candidate Donald Trump, the Washington Post reported Tuesday.

The secret order allowed the government under the Obama administration to monitor the communications of the adviser, Carter Page, as part of an investigation into potential links between Russia and the Trump administration.

Trump tweeted on March 4 that he had his “wires tapped in Trump Tower” during the campaign, for which critics bashed Trump, arguing that Obama himself could not order such a thing.

But the report validates that the FBI and Justice Department under the Obama administration were indeed monitoring an associate of the Trump campaign.

Terrible! Just found out that Obama had my "wires tapped" in Trump Tower just before the victory. Nothing found. This is McCarthyism! — Donald J. Trump (@realDonaldTrump) March 4, 2017

The Post reports:

The FBI obtained a secret court order last summer to monitor the communications of an adviser to presidential candidate Donald Trump, part of an investigation into possible links between Russia and the campaign, law enforcement and other U.S. officials said. The FBI and the Justice Department obtained the warrant targeting Carter Page’s communications after convincing a Foreign Intelligence Surveillance Court judge that there was probable cause to believe Page was acting as an agent of a foreign power, in this case Russia, according to the officials.

Any application for such an order would have had to “be approved at the highest levels of the Justice Department and the FBI,” the Post reported.

The report also states that the warrant provides evidence that the FBI “had reason to believe” that a Trump campaign adviser was in touch with Russian agents.

But it also states that “Page has not been accused of any crimes, and it is unclear whether the Justice Department might later seek charges against him or others in connection with Russia’s meddling in the 2016 presidential election.”

It also states that “most such investigations don’t result in criminal charges,” and that “an application for electronic surveillance under the Foreign Intelligence Surveillance Act need not show evidence of a crime.”

The Trump administration has called Page’s role “informal,” and Page has repeatedly denied any wrongdoing.

“This confirms all of my suspicions about unjustified, politically motivated government surveillance,” Page told the Washington Post on Tuesday.

“I have nothing to hide,” he said, and compared surveillance of him to the eavesdropping that the FBI and Justice Department conducted against civil rights leader Martin Luther King Jr.

Page himself told PBS NewsHour in February that he was a “junior member of the [Trump] campaign’s foreign policy advisory group.”

FBI Director James Comey revealed during a hearing last month in front of the House Intelligence Committee that the FBI had begun an investigation last July into Russian interference in the 2016 presidential elections, including whether there were any links with the Trump campaign.

Page worked in Moscow for Merrill Lynch a decade ago and had invested in Russian energy giant Gazprom, but said in a letter to Comey in September that he had sold his investment, according to the Post.

Former Director of National Intelligence James Clapper in March said that by the time he left in January, there was no evidence of any collusion between Russia and the Trump campaign.

Since the 90-day warrant was first issued, it has been renewed more than once by the FISA court, officials told the Post.

The Post‘s report also said Page submitted policy memos to the campaign and several times asked to meet with Trump, but that request was never granted.

Page participated in three dinners held for campaign foreign policy advisers.

Officials told the Post that Page is the only American to have his communications directly targeted with a FISA warrant in 2016 as part of the FBI’s probe into Russian interference.

However, then-incoming National Security Adviser Michael Flynn had his conversation with Russian Ambassador Sergey Kislyak illegally leaked to the Post in February.

While Kislyak was the likely target of the surveillance, Americans are supposed to have their identities kept anonymous, unless there is a request to “unmask” their identities.

Last month, House Intelligence Committee Chairman Devin Nunes (R-CA) said he saw evidence that members of Trump’s campaign were unmasked in incidental surveillance targeting foreigners.

Later it was revealed by blogger Mike Cernovich, and other outlets, that Obama’s National Security Adviser, Susan Rice, had ordered the unmasking of Trump transition team members.

FBI counterintelligence agents had been tracking Page three years before he became a Trump campaign adviser, the Post said.