The Obama administration has sought to block the release of documents related to its use of robot drones to strike suspected terrorists overseas, claiming that it can still not admit that the secretive programme of targeted killing exists.

The American Civil Liberties Union (ACLU) and the New York Times have both submitted freedom of information requests to the department of justice, the CIA and the Pentagon seeking information about the programme. They have now gone to court to try and force the government to answer those requests and release details of its activities.

However, in a motion filed just before midnight ET on Wednesday, the government asked for the cases to be dismissed, saying that to release information would hurt national security, even while still insisting it cannot admit any such programme of targeted killing exists.

"Whether or not the CIA has the authority to be, or is in fact, directly involved in targeted lethal operations remains classified," the government said in a court filing.

The move prompted the ACLU to label the continued refusal to acknowledge the use of drones to kill alleged terrorist leaders as "absurd" given that both President Barack Obama and his counter-terrorism adviser John Brennan have both made public references to it.

There have also been extensive leaks to the press, notably the New York Times, which recently ran a highly detailed story about a "kill list" that the Obama administration maintains.

"The notion that the CIA's targeted killing programme is still a secret is beyond absurd. 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," said Jameel Jaffer, ACLU deputy legal director.

US drone strikes have been credited by the administration with having badly damaged al-Qaida in places like Pakistan and Yemen, but are widely criticised by rights groups over the secrecy that makes it impossible to determine casualty figures, whether they are military or civilians, or on what legal basis the attacks occur.

Particular points of contention have been the New York Times' revelation that the administration considers any male of military age in a strike zone when a drone hits to be a militant and thus a legitimate target.

The deaths via drone attacks of American-born cleric Anwar al-Awlaki and his 16-year-old son – who was also an American citizen – have likewise earned condemnation from many human rights and civil liberties organisations.

The London-based Bureau of Investigative Journalism, which runs a drone-monitoring project, estimates that the US has used drones against targets in Pakistan up to 332 times in the past eight years, with a huge jump in activity under Obama. The Bureau believes up to 800 civilians may have been killed in the attacks. It has also monitored scores of drone attacks in Yemen and Somalia.

Jaffer called on the administration to be more open and demanded some form of public legal oversight. "We continue to have profound concerns that with the power the administration is claiming and with the proposition that the president should be be permitted to exercise this power without oversight by the courts. That the administration believes a power so sweeping should be exercised in secret is astounding," he said.

Despite its refusal to acknowledge a targeted killing programme exists there have been numerous public statements about the programme.

In April Brennan gave a speech where he said the programme "sometimes using remotely piloted aircraft" was carried out "in full accordance of the law" and used to strike specific al-Qaida terrorists.

Obama himself referenced the programme when asked about it in January. The president said the programme used only "precise, precision strikes against al-Qaida and their affiliates."