The CIA has opened an investigation into the conduct of its former director, David Petraeus, several days after he resigned.

General Petraeus quit his post last week after acknowledging an affair with his biographer, Paula Broadwell.

A CIA spokesman says the inquiry by the agency's inspector general would see if there are lessons to be learned.

Mrs Broadwell, 40, was found to have classified information in her possession.

In his first interview since resigning, Gen Petraeus told CNN on Thursday he did not give any national security-sensitive information to his lover.

The former head of US and Nato forces in Afghanistan became CIA director in September 2011.

The US intelligence agency said in a statement on Thursday: "At the CIA we are constantly reviewing our performance. If there are lessons to be learned from this case we'll use them to improve.

"But we're not getting ahead of ourselves; an investigation is exploratory and doesn't presuppose any particular outcome."

--Courtesy of BBC News