Special counsel Robert Mueller's investigation of Russian interference in the 2016 election has widened, The Washington Post reported, citing officials.

The probe now seeks to determine whether President Donald Trump attempted to obstruct justice, officials told the Post.

A spokesman for Trump's lawyer told NBC: "The FBI leak of information regarding the President is outrageous, inexcusable and illegal."

People familiar with the matter told the Post that the obstruction of justice probe started in the wake of Trump's firing of former FBI Director James Comey.

Mueller's team will interview Dan Coats, director of national intelligence, Mike Rogers, head of the National Security Agency, and Richard Ledgett, former deputy director of the NSA, the Post reported, citing five people briefed on the interview requests.

Read the full report in The Washington Post.

— NBC News contributed reporting.

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