The 39-year-old man was not in possession of arms or explosives. He had claimed to have an explosive device which he said could be set off with a mobile phone signal, Yildirim said.
'No political demands'
Earlier, officials said the man had stormed the cockpit, but Ali Sabanci, Pegasus's chief executive, said the cockpit was locked in accordance with international flight rules and the man had not succeeded in gaining access.
Yildirim said the man had not made any political demands and the reason he had wanted to divert the aircraft was under investigation.
The Boeing 737 aircraft left Diyarbakir at 5.40pm (14:40 GMT), Yildirim said. Pilots informed authorities of the attempt to divert the flight half-an-hour later.
The government-run Anatolia news agency said the man had been acquitted on charges of aiding the Kurdistan Workers Party (PKK), a separatist Kurdish group, in 1994.
However, an official at Ankara airport said the man appeared to have acted from personal motives, and may be mentally ill.
The hijacking comes six months after a Turkish man hijacked a Turkish Airlines flight on its way from Tirana, Albania, to Istanbul and forced its diversion to Italy.