Donald Trump exodus continues as interior secretary Ryan Zinke departs

US interior secretary Ryan Zinke is to leave the White House at the end of the year, says Donald Trump.

He is the latest in a series of high-profile departures from the president's administration.

Mr Trump posted on Twitter: "Secretary of the Interior @RyanZinke will be leaving the Administration at the end of the year after having served for a period of almost two years."

A replacement will be announced next week, he added.

Mr Zinke is facing an investigation into his travel, political activity and possible conflicts of interest.

The president did not give a reason for Mr Zinke's departure but the former Navy Seal and ex-congressman from Montana has come under scrutiny for his use of security details, chartered flights and a real estate deal.

Mr Trump said on Twitter: "Ryan has accomplished much during his tenure and I want to thank him for his service to our Nation."

Mr Zinke played a leading part in the president's efforts to reverse environmental regulations and promote domestic energy development.

His departure comes amid a shake-up of key staff as President Trump heads into his third year in office.

A batch of other top officials have left the White House, including a secretary of state, two national security advisers, an attorney general and the head of the US environment agency.

The president on Friday named budget director Mick Mulvaney as chief of staff to replace John Kelly.

Mr Zinke is one of a number of members of Mr Trump's cabinet to come under scrutiny over expenditures, including reports that his department was spending nearly $139,000 to upgrade three sets of double doors in his office.

He was also criticised for expensive US Park Police helicopter flights last year that allowed him to return to Washington for a horseback ride with vice-president Mike Pence, and several other flights on non-commercial aircraft.

Mr Zinke has been beleaguered by ethics probes, including one centred on a Montana land deal involving a foundation he created and being the chairman of an energy services company that does business with the interior department.

Mr Zinke's decision to block two tribes from opening a casino in Connecticut and his redrawing of boundaries to shrink a Utah national monument is also being investigated. He has denied any wrongdoing.

The interior secretary's departure makes him the ninth cabinet official to leave a post since Mr Trump entered the White House two years ago.