US President Joe Biden on Friday signed an executive order directing his government to review and release some documents related to the FBI's investigation into the September 11, 2001 terrorist attacks.

The order directs the Justice Department and other federal agencies to review documents and release declassified information over the next six months, Xinhua news agency reported. "We must never forget the enduring pain of the families and loved ones of the 2,977 innocent people who were killed during the worst terrorist attack on America in our history," Biden said in a statement.