The ruling party of the Turkish president, Recep Tayyip Erdoğan, has said it will seek a rerun of last week’s mayoral election in Istanbul, citing alleged irregularities.

Ali İhsan Yavuz, a deputy chairman for the Justice and Development (AKP) party, announced the decision on Tuesday after Turkey’s top electoral authority rejected a request for a full recount of votes in the 31 March elections.

Yavuz maintained there were “significant events and situations” that affected the outcome of the vote and said the party would use a right for an “extraordinary appeal”.

The AKP suffered a major setback in the local elections: opposition candidates won in Turkey’s capital, Ankara, and squeezed out the ruling party in Istanbul, where Erdoğan rose to power as mayor and which has been governed by his party and its Islamist predecessor for the last 25 years.

The AKP has demanded a recount, maintaining that the elections were marred by irregularities and alleged “organised crimes”. The opposition denounced the claims as a ploy to secure a rerun and has called on Erdoğan to concede that his party lost.

Turkey’s top electoral authority rejected a request for a full recount of votes in Istanbul on Tuesday, but did allow a recount of 51 ballot boxes in Istanbul’s 21 districts.

“It is incomprehensible how such a decision was taken given that there is so much irregularity,” Yavuz said on Twitter.

The electoral board is expected to confirm the election’s result at the end of the week.