By Stoyan Nenov
SOFIA, Jan 23 (Reuters) - Bulgaria's President Rumen Radev stepped down on Friday after the Constitutional Court approved his resignation, amid widespread speculation that he plans to launch his own political party to run in a looming parliamentary election.
Radev, 62, whose mandate had been due to expire next January, handed over his duties as head of state in a short ceremony to his vice president, Iliana Iotova, who becomes the first female president of the EU and NATO member state.
In Bulgaria, the president - elected by popular vote - is a mainly ceremonial role, though Radev has wielded considerable behind-the-scenes influence in a period of political instability that has seen seven parliamentary elections in just four years.
"This was my last day as president but my first day as a citizen who believes... that with joint efforts we can change Bulgaria, defend democracy, reaffirm the law and accelerate economic growth," Radev told reporters after the ceremony.
Scores of his supporters greeted Radev outside the presidency in central Sofia, some holding the red, green and white national flag.
Radev, who was elected president in 2016 and was nearing the end of his second and final mandate, has long been expected to form his own party with the aim of restoring stability and fighting graft in one of the European Union's poorest and most corrupt countries, which joined the euro on January 1.
But Radev, a former air force commander who polls suggest is the most popular politician in the Black Sea nation, has not yet directly confirmed his intentions.
"I want to tell you, when you ask about the upcoming (parliamentary) elections: They can't stop the wave, we are many, we are together, and our cause is shared," he said.
It now falls to Iotova to appoint a caretaker government and set a date for the parliamentary election following the collapse of Prime Minister Rosen Zhelyazkov's administration in December amid mass street protests over corruption and planned tax hikes.
(Reporting by Angeliki Koutantou; Editing by Sharon Singleton and Gareth Jones)
