USviewer: Sessions, a longtime U.S. senator who was an early and high-ranking player in President Donald Trump's campaign before becoming the country's top law enforcement official, announced the decision after several fellow Republicans in Congress suggested the move would be appropriate.
"I have recused myself in the matters that deal with the Trump campaign," Sessions told reporters at a hastily arranged news conference.
Sessions said he had been weighing recusal - ruling himself out from any role in the investigations - even before the latest twist of the controversy over ties between Trump associates and Russia that has dogged the early days of the Trump presidency.
The president backed Sessions, saying Democrats had politicized the issue and calling the controversy a "total witch hunt."
Sessions' announcement did nothing to quell concerns among congressional Democrats, a number of whom called for Sessions to step down.
Trump and Republicans who control Congress are trying to move past early administration missteps and focus on issues important to them, including immigration, tax cuts and repealing the Obamacare healthcare law.
U.S. intelligence agencies concluded last year that Russia hacked and leaked Democratic emails during the election campaign as part of an effort to tilt the vote in Trump's favor. The Kremlin has denied the allegations.
Sessions denied he had contact with Russian officials when he was asked directly during his Senate confirmation hearing to become attorney general whether he had exchanged information with Russian operatives during the election campaign.
He told reporters he was "honest and correct" in his response, although he acknowledged he "should have slowed down" and mentioned he had met with the ambassador in his role as a senator.
"I never had meetings with Russian operatives or Russian intermediaries about the Trump campaign," Sessions said, adding he felt he should not be involved in investigating a campaign in which he had had a role.
In a statement on Thursday night, Trump said Sessions "did not say anything wrong. He could have stated his response more accurately, but it was clearly not intentional."
Sessions' meetings with Russian Ambassador Sergei Kislyak were disclosed on Wednesday night by the Washington Post. Sessions received Kislyak in his Senate office in September and also met him in July at a Heritage Foundation event at the Republican National Convention that was attended by about 50 ambassadors.
Trump fired national security adviser Michael Flynn last month after disclosures that Flynn had discussed U.S. sanctions on Russia with Kislyak before Trump took office and that Flynn misled Vice President Mike Pence about the conversations.
The recusal means Sessions, a powerful member of Trump's inner circle, will not be briefed on details of any probe. Should the Federal Bureau of Investigation decide to move forward with charges, Sessions would not be in a position to weigh in on whether the Department of Justice should take the case.
House of Representatives Democratic leader Nancy Pelosi urged Sessions to resign and said "his narrow recusal and sorry attempt to explain away his perjury" were inadequate.
Adam Schiff, the top Democrat on the House intelligence committee, said Sessions' explanation for failing to tell the Senate about his meetings "is simply not credible." He called on Sessions to step down and said the Justice Department should name an independent prosecutor to investigate Russian interference.
Democrats on the House Judiciary Committee asked the FBI to launch a criminal investigation into Sessions' statements to Congress about his communication with Russian officials.
Sessions is one of many "subjects" of a government investigation of any contacts between the Trump campaign and Russia, two U.S. officials familiar with the probe said.
The officials, speaking on condition of anonymity, said Sessions was not now a "target" of the probe by the FBI, the Treasury Department, the CIA and the National Security Agency.
The investigation, one of the officials said, had a number of subjects because of the numerous contacts between associates of Trump, including Flynn, and the Russian Embassy in Washington as well as Russian and some Ukrainian businessmen and companies.
At least two other officials in Trump's campaign said they also spoke with the Russian ambassador at a conference on the sidelines of the July convention last July, USA Today reported on Thursday.
Trump's son-in-law and adviser Jared Kushner also met with Kislyak in December at Trump Tower in New York, an administration official said on Thursday, confirming a report in the New Yorker.
While there is nothing legally wrong with such meetings, the reported contacts raise questions about the White House's repeated statements that it knew of no further contacts with Russian officials beyond those by Flynn.
Trump has accused officials in former Democratic President Barack Obama's administration of trying to discredit him with questions about Russia contacts. The White House dismissed the disclosure of the Sessions meetings as a partisan attack, saying his contacts with the ambassador had been as a member of the Armed Services Committee.
Trump called frequently during his campaign for improved relations with Russia, drawing criticism from Democrats and some Republicans. Ties with Russia have been deeply strained in recent years over Moscow's military interference in Ukraine, military support for President Bashar al-Assad in Syria and President Vladimir Putin's intolerance of political dissent.
With his administration on the defensive over Russia, Trump's enthusiasm seems to have cooled, and his top foreign policy advisers have begun talking tougher about Moscow.
The Russian Embassy in Washington, shrugging off the uproar, said on Thursday it was in regular contact with "U.S. partners."