WASHINGTON: The US government has asked a federal court to reject lawsuits demanding the release of documents on CIA drone strikes targeting suspected militants abroad, saying the entire subject is “classified.”

Shortly before a midnight deadline on Wednesday, US government lawyers filed a brief to a district court in New York insisting on keeping a veil of secrecy around the drone campaign, which has killed numerous al Qaeda figures and associates in Pakistan, Yemen and Somalia.

“Whether or not the CIA has the authority to be, or is in fact, directly involved in targeted lethal operations remains classified,” the government brief stated.

The American Civil Liberties Union (ACLU) and The New York Times had filed lawsuits after having requested papers on the drone bombing campaign under the Freedom of Information Act.

The organisations had requested documents explaining the legal basis for the raids and the killing of terror suspects who are US citizens, such as the US-born cleric Anwar al-Awlaqi who was taken out last year in a drone strike.

But the government asked the court for a summary judgment to dismiss the lawsuits.

Government lawyers not only ruled out releasing documents related to the drone strikes, but argued that merely referring to the number or categories of documents posed a threat to national security.

“Even to describe the numbers and details of most of these documents would reveal information that could damage the government's counterterrorism efforts,” it said.

The ACLU called the government's argument “absurd,” saying the drone war was an open secret that government officials have boasted about to reporters.

“Senior officials have discussed it, both on the record and off. They have taken credit for its putative successes, professed it to be legal and dismissed concerns about civilian casualties,” ACLU deputy legal director Jameel Jaffer said in a statement.

“The public is entitled to know more about the legal authority the administration is claiming and the way that the administration is using it.” The ACLU called on President Barack Obama's administration to reveal information “about the process by which individuals, including American citizens, are added to government kill lists.” The Obama administration's brief to the court acknowledged the use of lethal force is “undoubtedly of the utmost public concern” but said it had to take into account legal prohibitions against the release of classified information.

To inform the public, the White House has organised a series of speeches by top officials, including President Barack Obama's chief counterterrorism adviser John Brennan, that have “set forth for the American people the legal analysis and process involved in the determination whether to use lethal force,” the government said.

US officials say the strikes by armed, unmanned aircraft have decimated al Qaeda's core leadership and saved American lives, but the raids have caused an unknown number of civilian casualties and sparked outrage in Pakistan.

Rights groups and commentators in the United States have questioned the precedent set by the drone campaign, saying it allows the US president to wield sweeping power to conduct a large-scale air war without public debate or judicial review.