Former FBI chief James Comey to testify in Russia probe on June 8

WASHINGTON, June 1 (Reuters) - Former FBI Director James Comey will testify before a Senate committee next Thursday as part of a probe into alleged Russian meddling in the U.S. presidential election and possible collusion with President Donald Trump's campaign.

The Senate Intelligence Committee said on Thursday it would hear from Comey, who was fired by Trump on May 9, first in an open session and then behind closed doors, which would afford senators a chance to discuss classified information.

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The former FBI chief is expected to testify on conversations he had with Trump in which the president reportedly pressured him to drop an investigation into former national security adviser Michael Flynn, one of several Trump associates who are drawing scrutiny in a series of probes about Russia and last year's U.S. election.

Russia has repeatedly denied any effort to interfere in the U.S. election, and Russian President Vladimir Putin on Thursday said some Russians might have acted on their own without their government's involvement.

Trump has denied any collusion between Russia and his campaign and has repeatedly questioned the U.S. intelligence finding that Putin led an operation that included computer hacking, fake news and propaganda intended to swing the election in Trump's favor over Democratic rival Hillary Clinton.

Comey was leading the FBI's probe into the allegations, and his firing sparked a political uproar. Facing rising pressure, the Justice Department earlier this month named another former Federal Bureau of Investigation chief, Robert Mueller, as a special counsel to investigate the allegations.

A number of congressional committees, in addition to the Senate intelligence panel, are also looking into the matter.

On Wednesday, the House of Representatives Intelligence Committee approved subpoenas for Flynn and Trump's personal lawyer, Michael Cohen, in connection with its probe.

In addition, the committee's Republican chairman, Representative Devin Nunes, who had recused himself from the panel's Russia investigation, also approved subpoenas to the CIA, FBI and National Security Agency for information relating to the "unmasking" of the names of Trump campaign advisers inadvertently picked up in top-secret foreign communications intercepts.

Committee aides complained he had acted unilaterally, and the top Democrat on the panel, Representative Adam Schiff, said Nunes' actions amounted to a breach of his recusal decision.

"Commitments to recuse himself have not been fully honored," Schiff told MSNBC.

Trump on Thursday backed Nunes' efforts to investigate actions by U.S. security and other officials who had served under previous President Barack Obama.

"The big story is the 'unmasking and surveillance' of people that took place during the Obama Administration," Trump said in a tweet.

(Additional reporting by David Alexander; Writing by Susan Heavey and Tim Ahmann; Editing by Lisa Von Ahn and Alistair Bell)