Bulgaria's prime minister has handed in his resignation in parliament after results showed his party losing badly in the presidential runoff, opening the way for an early parliamentary election.

Boiko Borisov's move Monday come after official results in Bulgaria show Socialist-backed candidate Rumen Radev, a former non-partisan air force chief, winning the presidential election.

The Central Election Commission said Monday that with 99.3 percent of the ballots counted, Radev won 59.4 percent of the vote, compared with 36.2 percent for the candidate of the ruling center-right party, Tsetska Tsacheva.

Radev, who will take office for a five-year term on Jan. 22, will face a possible rise in migrants from neighboring Turkey and growing tensions between Russia and the West.