Dhaka: The United Nations (UN) has encouraged the competent authorities in Bangladesh to investigate all the allegations regarding city polls and the opposition to use the democratic institutions to express its concerns.

UN Secretary General Ban Ki-moon is aware of BNP's decision of polls boycott and appealed to all parties to express their differences through peaceful means.

‘The Secretary-General is aware of the Bangladesh Nationalist Party's decision to boycott the Dhaka and Chittagong elections amid allegations of electoral fraud,’ said Farhan Haq, Deputy Spokesman for the UN Secretary-General in a regular briefing at its headquarters.

The Secretary-General reiterated his call on all political leaders to find a peaceful resolution to the current situation.

BNP boycotted the polls in Dhaka and Chittagong midway citing vote rigging and various types of irregularities in the polls.

Awami League-backed candidates Annisul Huq, Sayeed Khokon and AJM Nasir were unofficially elected mayors of three major city corporations in Dhaka and Chittagong in Tuesday's elections amid boycott by pro-BNP contenders.