Washington: The Pentagon has been running a secret multi-million dollar programme to investigate Unidentified Flying Objects (UFOs), US media report.

Only a small number of officials were aware of the programme, which began in 2007 and was reportedly closed in 2012. The New York Times says documents from the operation describe strange speeding aircraft and hovering objects. But scientists were doubtful, stressing that unexplained happenings were not necessarily proof of alien life.

The Advanced Aerospace Threat Identification Programme was the brainchild of Harry Reid, a retired Democratic senator who was the Senate majority leader at the time, reports BBC. He told the New York Times: "I'm not embarrassed or ashamed or sorry I got this thing going. I've done something that no one has done before."

Mr Reid - former senator for Nevada, home to the mythologised "Area 51" classified US Air Force base - later tweeted that the programme was a serious effort to get to truth amid "plenty of evidence to support asking the questions".