The Vatican has announced the resignation of its spokesman and his deputy, without giving any explanation.

Pope Francis "has accepted the resignation of the director and deputy director of the press office of the Vatican, Greg Burke and Paloma Garcia Ovejero, and named Alessandro Gisotti as acting director," it said in a statement.

American-born Mr Burke, a member of the ultra-conservative and influential Opus Dei movement, was appointed in July 2016. He was previously the deputy spokesman.

In a series of tweets, Mr Burke confirmed that he and Ms Garcia Ovejero would step down on January 1.

The 59-year-old had previously worked as a journalist in Rome for the weekly National Catholic Reporter, for Time magazine and for the US television network Fox News.

He was the second Opus Dei member to hold the post after Spain's Joaquin Navarro Valls, the powerful head of communications for Pope John Paul II.

Ms Garcia Ovejero, 43, a Spaniard, was the first woman to hold the number two post in the press office. She was previously Vatican correspondent for Spanish radio network Cadena COPE.

The resignations are the latest in a series of key staff changes within the pope's communications office, which also saw seasoned Vatican journalist Andrea Tornielli appointed as editorial head earlier this month.