House Republicans flexed their investigative muscle Tuesday, announcing two investigations into Obama administration dealings, including a 2010 uranium deal and the FBI’s handling of the probe of former Secretary of State Hillary Clinton’s emails.

The investigations, which will be conducted by three committees, were launched after President Trump endured months of criticism and congressional inquiry into Russian interference in the election last year and speculation that members of the president’s campaign team colluded with Moscow.

Democrats were infuriated by the announcements, saying the investigations were partisan-fueled distractions meant to divert attention from the ongoing Russia matter.

Mr. Trump, though, has long called for these kinds of probes into his predecessor, Mr. Obama, and his Democratic presidential opponent, Mrs. Clinton.

One of the investigations, run by the House intelligence and oversight committees, will dig into the circumstances surrounding a 2010 Obama administration deal that allowed a Kremlin-backed company to gain control of a huge chunk of America’s uranium supply.

Rep. Devin Nunes, California Republican and chairman of the House Permanent Select Committee on Intelligence, said lawmakers want to know if the Justice Department was investigating Russia’s atomic energy giant Rosatom even as another arm of the government, the Committee on Foreign Investment in the United States, signed off on the deal.

The State Department, run by Mrs. Clinton at the time, is one of the federal agencies that is part of the CFIUS.

The New York Times reported in 2015 that at least one individual involved in the transaction donated some $2.35 million to the Clinton Foundation. Those donations weren’t publicly disclosed by the Clintons despite an agreement Mrs. Clinton had with the Obama White House to identify all donors to the foundation.

“One of the things we are concerned about is whether or not there was an FBI investigation, was there a DOJ investigation, and if so, why was Congress not informed of this matter?” Mr. Nunes said.

Lawmakers said they have been trying to learn more about the deal for some time but decided they needed a formal investigation after hearing that a former FBI confidential informant tried to share information but was blocked from doing so because of a nondisclosure agreement with the Justice Department.

White House press secretary Sarah Huckabee Sanders on Tuesday called the investigation “a move in the right direction.”

But Mrs. Clinton told C-SPAN on Monday that the uranium story is “the same baloney they’ve been peddling for years, and there’s been no credible evidence by anyone.”

The second investigation announced Tuesday will probe how the Justice Department and former FBI Director James B. Comey handled an inquiry into Mrs. Clinton’s use of a secret email server to conduct government business while at the State Department.

House Judiciary Committee Chairman Bob Goodlatte, Virginia Republican, and House Oversight and Government Reform Committee Chairman Trey Gowdy, South Carolina Republican, said they want to know why Mr. Comey decided to publicly announce the investigation of Mrs. Clinton but not the ongoing investigation of campaign associates of Mr. Trump, why the FBI provided updates to Congress about reopening of the probe after additional emails were found, and why the FBI rather than the Justice Department took the lead in deciding not to criminally charge Mrs. Clinton.

Mr. Comey bucked Justice Department protocol with his July 2016 announcement that the case against Mrs. Clintonwas being closed without charges.

The FBI director later testified that he took the unusual step because he believed that a June 2016 airport tarmac meeting between Attorney General Loretta E. Lynch and Mrs. Clinton’s husband, former President Bill Clinton, had undermined the Justice Department’s credibility to independently investigate the case.

“Congress has a constitutional duty to preserve the integrity of our justice system by ensuring transparency and accountability of actions taken,” Mr. Gowdy and Mr. Goodlatte said.

In another development likely to gain traction with Republican investigators, The Washington Post reported Tuesday that the Clinton campaign and the Democratic National Committee helped pay for a dossier that contained salacious accusations about Mr. Trump’s connections to Russia.

The former British spy who compiled the dossier at some point turned over the information to the FBI, and Mr. Comey briefed Mr. Trump on the dossier following an intelligence briefing in January.

Mrs. Sanders, noting the development, said on Twitter, “The real Russia scandal? Clinton campaign paid for the fake Russia dossier, then lied about it & covered it up.”

Republican lawmakers have for months been trying to obtain information about who paid for the dossier, fearing that political opposition research was used as the basis for a foreign surveillance order.

White House press secretary Sarah Sanders, noting the development, said on Twitter, “The real Russia scandal? Clinton campaign paid for the fake Russia dossier, then lied about it & covered it up.”

Xochitl Hinojosa, communications director for the Democratic National Committee, said in a statement, “Tom Perez and the new leadership of the DNC were not involved in the decision-making regarding Fusion GPS, nor were they aware that Perkins Coie was working with the organization.”

Rep. Debbie Wasserman Schultz of Florida led the DNC at the time.

“But let’s be clear: There is a serious federal investigation into the Trump campaign’s ties to Russia,” Ms. Hinojosa said.

Mrs. Sanders, noting the development, said on Twitter, “The real Russia scandal? Clinton campaign paid for the fake Russia dossier, then lied about it & covered it up.”

The president’s eldest child, Donald Trump Jr., called the dossier story “interesting.”

“You know if the Washington Post can’t sweep this under the rug it’s a big deal,” he tweeted.