The West Australian newspaper said British officials, with the aid of Australian representatives, found and "extracted" the 41-year-old from his jail and put him on a plane to Istanbul.
Perth-based Smitheringale said he was relieved "to see the sun again".
"28 days in a Libyan militia prison. The first 27 were the hardest," he said on his blog.
"These people are definitely not to be trifled with.
"It would be inappropriate of me to elaborate on the details of my capture and extraction and as I'm still in country."
Smitheringale, who describes himself as a "grown up version of Action Man", had previously attempted to become only the third person in history to reach the North Pole unassisted in 2010.
But he had to be rescued by the Canadian military after activating a distress beacon.