The Associated Press has described the U.S. government's secret seizure of its journalists' telephone records as a "massive and unprecedented intrusion".

According to BBC News, chief executive Gary Pruitt said AP was told the justice department had gathered records of outgoing calls from more than 20 phone lines.

Pruitt said there could be "no possible justification for such an overbroad collection".

The justice department has provided no explanation for the seizure. However, officials have previously said the U.S. Attorney's Office in the District of Columbia was conducting a criminal investigation into information contained in an AP story last year.

Published in May 2012, the article was about a CIA operation in Yemen that foiled an al-Qaeda plot to blow up a U.S.-bound airplane.

Records for the phone numbers of five reporters and an editor who were involved in the AP story were among those obtained in April and May 2012.

AP said the seizure of records for general switchboard numbers and a fax line at its offices in New York, Hartford, in Connecticut, Washington DC and the House of Representatives was unusual and largely unprecedented.

"There can be no possible justification for such an overbroad collection of the telephone communications of the Associated Press and its reporters," Pruitt wrote in a letter to US Attorney General Eric Holder.

"These records potentially reveal communications with confidential sources across all of the newsgathering activities undertaken by the AP during a two-month period, provide a road map to AP's newsgathering operations, and disclose information about AP's activities and operations that the government has no conceivable right to know."

It is not clear if the records seized included incoming calls or the duration of the calls. Nor is it clear whether a judge or grand jury approved the subpoenas, the BBC says.

News organizations are normally notified in advance if the government is seeking such information and are given time to negotiate.