WASHINGTON: Recent revelations about clandestine US drone campaigns against al Qaeda and other militants are not part of two major leak investigations being conducted by federal prosecutors, sources familiar with the inquiries said.

Most detailed information on the drone wars, which were initiated by the George W. Bush administration but expanded by President Barack Obama, is highly classified, officials said.

But Obama and top administration officials, including White House counter-terrorism Chief John Brennan, recently have been alluding more openly to drone operations in public remarks, and detailed news coverage has been widespread.

The CIA has not filed a “crime report” with the Justice Department over reports about Obama's drone policy and a US “kill list” of targeted militants, an action which often would trigger an official leak investigation, two sources familiar with the matter said.

They requested anonymity to discuss sensitive information.

By contrast, the CIA did file a “crime report” following publication by the Associated Press last month of a report disclosing the foiling of a plot by Yemen-based al Qaeda in the Arabian Peninsula to attack an airliner using a newly designed underwear bomb, sources said.

Officials said the second leak investigation involves a series of revelations in a book and article by a New York Times journalist about the alleged role of US agencies in cyber-warfare activities against Iran.

These include the creation and deployment of a virus known as Stuxnet which attacked Iranian uranium enrichment equipment.

US officials declined to say which of the two prosecutors designated by Attorney General Eric Holder was investigating which alleged leak. Holder told a Senate committee on Tuesday the US attorneys involved, in Washington and Baltimore, were each looking into “separate matters.”

The US National Security Agency and its cyber-warfare affiliate, the US Cyber Command, have headquarters at Fort Meade, a military installation in Maryland between Baltimore and Washington. Officials said this suggests that the US attorney in Baltimore is working on the cyber-warfare leak case.

Representatives of Baltimore-based US Attorney Rod Rosenstein and the NSA declined to comment.

Republican Criticism

Some of the Obama administration's Republican critics harshly questioned Holder's decision to assign the leak inquiries to US attorneys - who normally operate under supervision of the Justice Department headed by Holder - and demanded a more independent investigation.

“One of the problems with the Attorney General's decision is that each prosecutor will investigate a separate leak - one on the AQAP bomb plot and one on the Stuxnet story,” said Senator Saxby Chambliss, Republican vice-chairman of the Senate Intelligence Committee.

“So, it appears that no one will investigate any of the other recent leaks and no one will be taking a high-level look at whether there is a pattern to these leaks. We need one lead Special Counsel in charge of all of the related leaks,” he said.

Current and former US officials said one key reason why the CIA might not have sought a criminal investigation into the latest round of drone-related disclosures - which included a lengthy New York Times article - may be that so much has been written and said publicly about the US drone campaign in the past several months.

Reuters published a story in October containing some details about the “kill list” and how it was assembled.

Numerous media have reported extensively about individual drone attacks, including a strike in Pakistan last week that killed al Qaeda's alleged second-in-command, Abu Yahya al-Libi.