The president's long-time personal aide John McEntee has been fired by the White House, according to US media.

Mr McEntee, who served as an aide since early in the campaign, was reportedly escorted by security and was not permitted to collect his belongings.

President Donald Trump's re-election campaign announced on Tuesday Mr McEntee would join as a "senior adviser for campaign operations".

The announcement came on the same day Mr Trump fired his secretary of state.

Mr McEntee was fired amid a US Department of Homeland Security investigation against him for financial crimes, CBS News reports.

US media reported his abrupt exit came about due to difficulties in obtaining a full security clearance.

The former Fox News producer joined Mr Trump's presidential campaign in the early months and had since been seen by his side at many events.

The Wall Street Journal first reported Mr McEntee's sacking, citing a security issue.

Mr McEntee, who was most recently seen travelling to Pennsylvania with Mr Trump for a rally on Saturday, was expected to join the president in California on Tuesday before his sacking.

His exit follows another original Trump campaign aide. White House Communications Director Hope Hicks resigned last month.

Mr Trump's re-election campaign manager, Brad Parscale, announced on Tuesday Mr McEntee would rejoin the 2020 effort along with Katrina Pierson, a former Trump campaign spokeswoman.

"As we build out our operations for the 2018 midterm elections and the 2020 re-election campaign, we are pleased to welcome back two outstanding members of our 2016 team," Mr Parscale said on Tuesday.

"We need the help of proven leaders such as... John to promote the President's growing portfolio of achievements across the country."