Then- National Security Advisor of the United States John Bolton holds a news conference during his visit to Ukraine, Kyiv, capital of Ukraine, August 24, 2018.

Former National Security Advisor John Bolton returned to Twitter on Friday, and immediately accused the White House of locking him out of his account.

"Since resigning as National Security Advisor, the @WhiteHouse refused to return access to my personal Twitter account," tweeted Bolton, whose account had been dormant since he left the White House in September.

"Out of fear of what I may say?" asked Bolton, who has been asked by Democrats to testify in the House impeachment inquiry into President Donald Trump.

"To those who speculated I went into hiding, I'm sorry to disappoint!" he tweeted.

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The White House, Bolton said in a follow-up later Friday, "never returned access to my Twitter account."

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Bolton's last tweet before his two-month hiatus said that he had offered his resignation to Trump, contradicting the president, who said that he had fired Bolton.

Bolton was asked to appear for a closed-door deposition in November before the House Intelligence Committee as part of the impeachment probe of whether Trump abused his power by pressuring Ukraine to announce political investigations.

But Bolton did not show up to testify — though he was reportedly still willing to testify depending on the outcome of a separate court fight. An Intelligence Committee official told CNBC at the time that Bolton's lack of full cooperation amounted to more evidence of Trump's obstruction of Congress in its impeachment inquiry.

Trump's former top Russia expert Fiona Hill testified that Bolton was concerned about the efforts by U.S. Ambassador Gordon Sondland and others to get Ukraine to agree to the investigations during a July meeting.

After that meeting, Bolton told Hill to "go to the [National Security Council] lawyers, to John Eisenberg to basically say, 'Ambassador Bolton is not part of whatever drug deal Sondland and Mulvaney were cooking up,'" according to Hill's testimony.

Earlier Friday, Bolton said, "We have now liberated the Twitter account, previously suppressed unfairly in the aftermath of my resignation as National Security Advisor."

He added cryptically: "More to come....."

A person familiar with the situation told CNBC that Bolton had agreed to give the password for his Twitter account to the government when he joined the Trump administration — but he never intended to relinquish the account forever.

Since leaving the administration, Bolton has been fighting to regain control of the @AmbJohnBolton handle, said the person, who did not know how Bolton got his account back. That verified account currently boasts more than 755,000 followers.

In an interview on Fox News, Trump denied that the White House froze Bolton's account.

"Of course not," Trump responded. "No, I actually had a good relationship with John. We disagreed on some things and some methods but I actually had a good relationship."

The White House did not respond to CNBC's request for comment on Bolton's suggestion that his Twitter account had been suppressed. Twitter did not immediately provide comment.