ANKARA - Turkish riot police fired tear gas and stormed the main opposition party's headquarters Sunday to evict its ousted leadership, fueling a deepening crisis at the heart of Turkey's democracy.

Clouds of tear gas billowed inside the Republican People's Party (CHP) building as officers broke through a makeshift barricade. No injuries were reported.

A Turkish court ousted CHP leader Ozgur Ozel on Thursday, annulling his 2023 election over irregularities and reinstating former chair Kemal Kilicdaroglu, who lost to President Tayyip Erdogan in a national election that year.

Analysts see the ruling as a test of democracy versus autocracy for NATO member Turkey. Financial markets tumbled Thursday on fears of democratic backsliding, then rebounded Friday.

"We are under attack," Ozel said in a video message as police entered. After emerging from the building, he vowed the CHP would now be "on the streets, in the squares, marching towards power."

Ozel led supporters on a march to parliament, where he addressed thousands who chanted against Kilicdaroglu. "Until this struggle frees the party from occupation, our headquarters is here," he said.

The ousted leadership condemned the court ruling as a "judicial coup." Ozel has called for a new party congress as soon as possible. Turkey's next national election is set for 2028, but analysts said the ruling raises chances of an early vote.

The government denies using courts to target political rivals, insisting the judiciary is independent.