Former CIA Director David Petraeus has made a secret appearance before US Congress after sneaking past reporters.

Petraeus appeared behind closed doors before the House and Senate intelligence panels the week after quitting his CIA post because of an extramarital affair.

Petraeus, a retired Army four-star general, slipped in and out of the closed sessions unseen by a swarm of media. Capitol police cleared journalists and others from hallways where the former CIA director might have been spotted.

'You can blame it on us,' Senator Dianne Feinstein, Democratic chairwoman of the Senate Intelligence Committee, told reporters who complained about not even seeing Petraeus.

Although he has left the CIA, Petraeus was asked to testify about September's deadly attack on the US diplomatic mission in Benghazi, Libya, in part because he had gone to Libya before his resignation to interview people about what happened in Benghazi on September 11.

'The general was both eager and willing to give us his views on this, and his experience on it, and that's very much appreciated. ... We didn't want to make it any more difficult for him,' Feinstein said.

Lawmakers appeared to treat the question of Petraeus' personal life with kid gloves. They said the questioning was sometimes awkward against the backdrop of the Broadwell scandal and because some of them have known Petra.