WASHINGTON: Four members of Donald Trump's inner circle on Thursday received subpoenas to appear before a congressional committee to shed light on what exactly the former president said and did on the day rioters stormed the US Capitol earlier this year.

Congressional investigators are closing in on the Republican billionaire, whom Democrats accuse of being responsible for the deadly attack on the seat of US democracy in Washington on January 6.

The Democratic-controlled special investigatory committee, which Trump has dismissed as biased, is particularly interested in Mark Meadows, Trump's chief of staff at the time.

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"It appears you were with or in the vicinity of President Trump on January 6, had communications with the president and others on January 6 regarding events at the Capitol and are a witness regarding activities of that day," Representative Bennie Thompson, who chairs the committee, wrote in a letter to Meadows.

Dan Scavino, another of Trump's close advisors who was subpoenaed, is believed to have been with Trump on January 5 during a discussion on how to convince members of Congress not to certify the November presidential election victory of Joe Biden over Trump.

Several hundred rioters stormed the Capitol building as Congress was in the process of formally certifying Biden's victory, falsely claiming the vote had been stolen.

The stunningly violent and chaotic assault left five people dead, including a Capitol police officer.

Trump was impeached by the Democratic-controlled House in January for inciting insurrection but was acquitted by the Senate.

Trump has consistently refused to acknowledge his defeat to Biden and continues to make unfounded claims that he won the election.

Other Trump associates summoned by the committee include Steve Bannon and Kashyap Patel.

The committee wants the four men provide a set of documents by October 7, and testify before Congress the following week.