The BBC's Mark Davenport: "Sinn Fein are rather annoyed"

The brother of Alliance Party leader Lord Alderdice was elected as Lord Mayor of Belfast, a civic and ceremonial post, after defeating Sinn Fein's Alex Maskey.

He is only the second Alliance politician to hold the office and pledged to bridge the "religious, political, social and economic" divide between the communities.

But the election of Dr Alderdice has reportedly angered the City Council's Sinn Fein block which, as the joint largest party, had hoped to succeed the Social Democratic and Labour Party's Alban McGuinness.

All parties on the council backed the election of Dr Alderdice with the exception of Sinn Fein and the anti-Stormont Agreement Democratic Unionists.

Most mayoral elections in UK councils are made by mutual agreement between local parties.

Lord Alderdice: Brother only second Alliance mayor of Belfast

Dr Alderdice said: "With the world media focusing on this city since the Good Friday Agreement and the referendum, I want to use the Lord Mayor's office to promote a united, energetic, dynamic, positive and creative force we all know it could be."

He added that he would ensure that all important city council posts are shared among the parties and he opposed moves to block Sinn Fein from holding office.

Shortest Mayoral term

Meanwhile in Londonderry, the new mayor of the city is expected to announce his resignation after just one day in office, a record for UK local government.

Former Royal Ulster Constabulary officer Joe Miller, a member of the DUP, has said he has been forced to reconsider his position as the ceremonial head of the council after fellow councillors elected a Sinn Fein candidate as his deputy.

The row over the election of Sinn Fein's Lynn Fleming as Deputy Mayor took a further twist after Ulster Unionist councillor Andrew Davidson supported the move.