"We made our objection to the Supreme Election Board cancelling the candidacy of our Van Greater City Mayor Abdullah Zeydan and giving the mandate to the AKP candidate," the DEM party said in a statement.

DEM's Abdullah Zeydan had garnered over 55 percent of the vote in Van in local elections on Sunday.

But the regional electoral commission said he was ineligible to stand, handing city hall to a candidate from President Recep Tayyip Erdogan's ruling Justice and Development Party (AKP) who scored only 27 percent.

Their decision followed the last-minute reversal of a court verdict that had restored his right to stand for election.

Zeydan, who had been elected on the HDP (now DEM) ticket in 2015, was arrested in 2016 after criticising the Turkish army's air campaign against outlawed Kurdish militants in the Kurdish-majority southeast.

Violent protests against his ouster lasted through the night in Van province, which lies on Turkey's eastern border with Iran.

The local governor's office banned all demonstrations for 15 days after violent scuffles spread to several cities in the region, with some protesters setting police barricades ablaze.

Interior Minister Ali Yerlikaya said 89 people were detained, 26 of them in Van province, for joining unauthorised rallies and chanting slogans in praise of a "separatist terror organisation", referring to the Kurdistan Workers' Party (PKK) blacklisted by Turkey and its Western allies.

In the southeastern Yuksekova district of Hakkari, 29 people were detained after violent clashes between protesters and police late Tuesday.

DEM -- accused by authorities of links to the PKK -- on Sunday claimed the mayorships of large towns in Turkey's Kurdish-majority southeast, including the region's largest city Diyarbakir.

The movement is also the third-largest party in Turkey's national parliament.

Fellow opposition party CHP, which made major gains in the local elections and held control of Istanbul and other big cities, has backed DEM in its battle against the Van ruling.

A delegation from the party is due to visit Van on Wednesday, the CHP said.