The FBI and Justice Department on Thursday held a pair of high-level briefings for lawmakers in an effort to ease Republican pressure over the Russia investigation, amid President Trump’s outcry over revelations that a confidential informant made contact with several of his advisers during the 2016 campaign.

The White House-brokered briefings were expanded at the 11th hour to include an afternoon session for bipartisan members of Congress, but that gesture did little to muffle criticism from Democrats who said the sessions played into the hands of those trying to undermine the Robert Mueller probe.

By the time both sessions were concluded Thursday afternoon, each side appeared to be digging in.

“Nothing we heard today has changed our view that there is no evidence to support any allegation that the FBI or any intelligence agency placed a spy in the Trump campaign or otherwise failed to follow appropriate procedures and protocols,” Rep. Adam Schiff, D-Calif., the top Democrat on the Intelligence Committee, said after the meeting.

Meanwhile, House Speaker Paul Ryan, R-Wis., defended the House Intelligence Committee’s requests for records from the DOJ about the Russia investigation, following several weeks of a contentious back-and-forth between House Intelligence Committee Chairman Devin Nunes, R-Calif., and DOJ officials.

“Inherent in the committee’s work is the responsibility to ask tough questions of the executive branch,” Ryan said. “That is why we have insisted and will continue to insist on Congress’s constitutional right to information necessary for the conduct of oversight.”

Before the meetings began, Trump drew more attention to reports alleging that the FBI infiltrated his presidential campaign.

“Starting to look like one of the biggest political scandals in U.S. history,” Trump tweeted Thursday. “SPYGATE - a terrible thing!”

White House press secretary Sarah Sanders said White House Chief of Staff John Kelly and White House lawyer Emmet Flood made brief remarks during the briefings to convey "the president’s understanding of the need to protect human intelligence services and the importance of communication between the branches of government." She also said they relayed Tump’s “desire for as much openness as possible under the law.”

Democrats criticized Flood’s appearance at the beginning of the briefings, with Schiff calling it “entirely improper.” Flood recently joined Trump's legal team to help with the Russia investigation.

“His presence only underscores what Rudy Giuliani said: the president’s legal team expects to use information gleaned improperly from the Justice Department or the President’s allies in Congress to their legal advantage,” Schiff said.

The noon meeting at the Justice Department included Deputy Attorney General Rod Rosenstein; FBI Director Christopher Wray; Director of National Intelligence Dan Coats; Nunes; House Oversight and Government Reform Chairman Trey Gowdy, R-S.C.; Schiff and Ryan.

A second meeting took place later in the afternoon on Capitol Hill between Rosenstein, Wray, Coats, Gowdy, Republican and Democratic leaders from both the House and Senate, as well the top lawmakers from their intelligence panels.

The announcement of a second meeting came after criticism from Democrats who said the briefing should have been given to a bipartisan group of "Gang of 8" lawmakers -- as opposed to just Nunes and Gowdy, as initially scheduled.

“While it's a good thing that the Gang of Eight will be briefed, the separate meeting with a known partisan whose only intent is to undermine the Mueller investigation makes no sense and should be called off,” Senate Democratic leader Chuck Schumer, D-N.Y., said. “What is the point of the separate briefing if not to cause partisan trouble?”

Schumer was referring to Nunes, an ardent Trump supporter, who has been demanding information on an FBI source in the Russia investigation.

Late Sunday, the DOJ asked its watchdog to investigate whether there was inappropriate surveillance.

"If anyone did infiltrate or surveil participants in a presidential campaign for inappropriate purposes, we need to know about it and take appropriate action," Rosenstein said in a statement announcing the move.

The meetings themselves have been controversial since they were first announced this week.

In initially announcing the Nunes-Gowdy meeting Tuesday, Sarah Sanders said no Democrats had been invited because they had not requested the information.

White House spokesman Raj Shah initially told Fox News that a separate meeting between the "Gang of 8" and Justice Department, law enforcement and intelligence officials would take place after Congress returns from its Memorial Day recess.

However, Shah said in an updated statement late Wednesday that the White House was "working" to schedule a "Gang of 8" briefing before the recess.

In another twist, three Republican senators -- Chuck Grassley of Iowa, the chairman of the Judiciary Committee; Lindsey Graham of South Carolina; and John Cornyn of Texas -- sent a letter to Rosenstein and Kelly Tuesday expressing interest in attending the meeting.

"I want to find out what's going on," Graham said Wednesday. " ... I don't think we've ever had a circumstance like this where during the campaign the FBI felt like they had to apparently, I don't know whether it’s true or not, have a confidential informant engage in a campaign so somebody needs to figure out if you do this again, how you do it or if you do it all."

For his part, Gowdy told Fox News Wednesday that "I don't care who comes" to the meeting.

"The only thing I'd ask, if you show up, show up with an open mind and closed lips," Gowdy told Fox News' "The Daily Briefing." "In other words don't leak like a sieve when we get through with the meeting ... But it's not my meeting and I don't publish the invite list."

Fox News' Samuel Chamberlain, Mike Emanuel, Amy Wehinger and the Associated Press contributed to this report.