WASHINGTON, July 11 (Reuters) - The New York Times reported on Saturday that the U.S. Justice Department has ordered several of its journalists to testify before a federal grand jury after they published reports about security concerns related to the new presidential plane gifted by Qatar to U.S. President Donald Trump.

The newspaper reported that subpoenas were issued on Friday requiring the journalists to appear before a grand jury next Wednesday to testify "regarding an alleged violation of federal criminal law."

The newspaper reported that the summonses were issued by Jay Clayton, the U.S. Attorney for Manhattan, and in some cases delivered by federal employees to the journalists' homes.

The move was described as "an extraordinary escalation in President Trump's attempts to threaten and intimidate independent news organizations."

A Justice Department spokesman neither confirmed nor denied the subpoenas in a statement sent to Reuters, but said the administration is not targeting journalists but is concerned about some leaking classified information. The White House referred all questions to the Justice Department.

Trump said on Wednesday that he would use an old presidential plane "for the good old days" to travel from Ankara to the Royal Air Force base at Mildenhall in Britain, while the new plane stopped at the same base so that American military personnel there could inspect the aircraft.

A video late Wednesday showed Trump boarding the new presidential plane, a gift from Qatar, at the British base as it prepared to fly to the United States.