The US Justice Department maintained a secret database of Americans' international phone calls for more than a decade before ending the program in 2013, The Wall Street Journal reported Friday.

The newspaper said the spying program was uncovered in a court document filed Thursday in the case of a man accused of conspiring to illegally export electronic equipment to Iran.

The paper cited a Drug Enforcement Administration official as saying in a filing that the agency had used administrative subpoenas rather than federal court orders to scoop up metadata of calls "determined to have a demonstrated nexus to international drug trafficking and related criminal activities."

A US Justice Department official confirmed to AFP that the program had been suspended in September 2013 before being shut down.

"The program was suspended in September 2013 and ultimately terminated," Justice Department official Marc Raimondi said.

"It has not been active nor searchable since September 2013, and all of the information has been deleted. The agency is no longer collecting bulk telephony metadata from US service providers."

Revelations about widespread US surveillance programs used in counter-terrorism efforts emerged in 2013, sparking protests from civil liberties groups and fueling a national debate about the extent of government snooping.

The metadata gathered covers information such as the number dialed and the duration of a call but not the content of the conversations themselves.

In 2006, USA Today revealed that the National Security Agency was secretly gathering data from major operators on communications between parties in the United States and overseas.