Turkish President Recep Tayyip Erdogan declared victory Sunday in a historic runoffvote that posed the biggest challenge to his 20 years of transformative but divisive rule.

The 69-year-old leader overcame Turkey’s biggest economic crisis in generations and the most powerful opposition alliance to ever face his Islamic-rooted party to take an unassailable lead.

Near complete results showed him leading secular opposition rival Kemal Kilicdaroglu by four percentage points.

“We will be ruling the country for the coming five years,” Erdogan told his cheering supporters from atop a bus in his home district in Istanbul. “God willing, we will be deserving of your trust.”

Turkey’s main cities erupted in jubilation as Erdogan spoke.

Traffic on Istanbul’s iconic Taksim Square ground to a halt and huge crowds gathered outside his presidential palace in Ankara.

The opposition leader promised to make a statement later Sunday.

Turkey’s longest-serving leader was tested like never before in what was widely seen as the country’s most consequential election in its 100-year history as a post-Ottoman republic.

Kilicdaroglu cobbled together a powerful coalition that grouped Erdogan’s disenchanted former allies with secular nationalists and religious conservatives.

He pushed Erdogan into Turkey’s first runoff on May 14 and narrowed the margin further in the second round.

Opposition supporters viewed it as a do-or-die chance to save Turkey from being turned into an autocracy by a man whose consolidation of power rivals that of Ottoman sultans.

“I invite all my citizens to cast their ballot in order to get rid of this authoritarian regime and bring true freedom and democracy to this country,” Kilicdaroglu said after casting his ballot on Sunday.

Opposition gamble

Kilicdaroglu re-emerged a transformed man after the first round.

The former civil servant’s message of social unity and freedoms gave way to desk-thumping speeches about the need to immediately expel migrants and fight terrorism.

His right-wing turn was targeted at nationalists who emerged as the big winners of the parallel parliamentary elections. (AFP)