Former Catalan separatist leader Carles Puigdemont defied an arrest warrant to appear at a rally in the Spanish city of Barcelona on Thursday after seven years of self-imposed exile, and then vanished before police could arrest him.

Amid a heavy police presence, Puigdemont spoke to a crowd of thousands of followers in the Catalan capital from a platform near the Catalan parliament before disappearing backstage.

He told the crowd he aimed to revive the independence drive that plunged Spain into political crisis seven years ago.

"Today, many thought they'd be celebrating my arrest, and thought that this punishment would dissuade us - and you," he said.

"Today I came to remind them that we are still here! We are still here because we have no right to quit."

Senior officials of his Junts party, including parliament speaker Josep Rull, and members of the moderate separatist Esquerra Republicana de Catalunya which currently runs the regional government led a march to the Catalan parliament after the rally as journalists tried to spot whether Puigdemont was among them.

A debate to swear in Socialist Salvador Illa as

Catalonia's new president, ending a decade of separatist rule, began amid confusion and speculation about Puigdemont's whereabouts and how he could have vanished in plain sight.

"We had to see how the state allowed this criminal to hold a rally," said Ignacio Garriga, secretary general of the far-right Vox party, told reporters outside the Catalan parliament. "We don't understand why he hasn't been arrested yet".

A Catalan Interior Ministry spokesperson confirmed Puigdemont had evaded capture. "I can confirm Puigdemont has not been detained yet," she said. "I can confirm roadblocks have been set up to find him."

Puigdemont, 61, fled to Belgium seven years ago after a failed secession bid and has been living in exile ever since. He is now likely to be detained over an outstanding arrest warrant for alleged embezzlement, which he denies.