By Ezgi Erkoyun and Humeyra Pamuk
ISTANBUL (Reuters) - Turkish President Tayyip Erdogan attacked Istanbul's ousted mayor on Tuesday, days before a crucial re-run of the municipal vote, accusing him of being aligned with a U.S.-based cleric blamed by Ankara for orchestrating a 2016 failed coup.
Ekrem Imamoglu, from the main opposition Republican People's Party (CHP), narrowly beat the candidate of Erdogan's AK Party in a March mayoral contest. After AK Party appeals, the election commission annulled the result and ordered a re-run on June 23.
That decision has brought international criticism and accusations from Turkey's opposition of eroding democracy. It has also unnerved financial markets and thrown a spotlight on the AKP's management of Turkey's largest city and commercial hub during its long years in power.
After staying relatively quiet on the mayoral race in recent weeks, Erdogan said on Tuesday Imamoglu was in cahoots with the network of Fethullah Gulen, the Muslim cleric accused by Turkey of masterminding the July 15, 2016 failed coup.
"Where does he stand? He is with the Gulenists," said Erdogan, speaking on top of a bus in the working class Istanbul district of Sultangazi, referring to followers of Gulen.
Erdogan cited tweets sent by Imamoglu on the day of the coup but offered no other evidence.
Imamoglu has denied any links with the group. In one tweet posted on July 16, 2016, Imamoglu said Turkey should overcome the attempted coup by pursuing democracy and peace. It was not immediately clear which tweet Erdogan alluded to.
A spokeswoman for Imamoglu was not immediately available on Tuesday for comment.
The AKP's loss of Istanbul in the March 31 local elections was one of the biggest setbacks for Erdogan since his Islamist-rooted party swept to national power in 2002. The AKP also lost control of the capital Ankara.
Some commentators said Erdogan had ratcheted up his rhetoric after a televised debate on Sunday between Imamoglu and the AKP's mayoral candidate, Binali Yildirim, a former prime minister and close ally of the president.
Polling company Mak Danismanlik said Imamoglu had bested his rival in the debate, earning a lead ahead of Sunday's vote.
(Reporting by Humeyra Pamuk; Editing by Gareth Jones)