Former Trump White House officials Mark Meadows and Steve Bannon have been called to appear before the US House of Representatives Select Committee investigating the deadly January 6 riot at the US Capitol.
Former White House Deputy Chief of Staff Dan Scavino and former Defence Department official Kash Patel were also subpoenaed and instructed to produce materials and appear for depositions, committee Chairman Bennie Thompson said in a statement.
Meadows, a former congressman, served as former president Donald Trump's White House chief of staff, while Bannon was a White House adviser.
Patel said in a statement he was "disappointed, but not surprised" the committee issued a subpoena before seeking his voluntary co-operation.
A representative for Meadows said he declined to comment, while Bannon and Scavino could not be reached.
Meadows and Scavino have been instructed to appear for depositions on October 15, and Bannon and Patel a day earlier.
A mob of Trump supporters stormed the Capitol as Congress was meeting to certify Joe Biden's election victory, delaying that process for several hours as then-vice president Mike Pence, members of Congress, staff and journalists fled from rioters.
Nearly 600 people have been arrested in connection with the attack, which was the worst violence at the seat of the US government since the British invasion during the War of 1812.
House Democrats formed the committee of inquiry over objections from Trump's fellow Republicans in the House. Two Republicans are on the committee, Liz Cheney and Adam Kinzinger.
They are among 10 House Republicans who voted to impeach Trump on a charge of inciting the violence in a fiery speech repeating false claims that his defeat was the result of widespread fraud. The Senate later acquitted him.
"We will fight the subpoenas on executive privilege and other grounds," Trump said in a statement.
Australian Associated Press