Four men have been arrested in a nationalist area of Co Derry after the PSNI discovered a bomb in a vehicle last night.

Police said the viable device was discovered after officers investigating dissident republican activity stopped a car in the Westway area of Creggan.

The discovery comes ahead of a visit by US Secretary of State Hillary Clinton, who will speak at Stormont and visit the new Titanic Centre later.

Two men, aged 47 and 49, were arrested at the scene at around 8.40pm. Two others, also in their 40s, were arrested later.

A PSNI spokeswoman said the men were taken to Antrim Serious Crime Suite for questioning.

A number of homes had to be evacuated as army bomb disposal experts made the device safe.

Separately, a small crowd of demonstrators clashed with the PSNI in Ballymena, Co Antrim, after the protesters gathered to show their anger over the union flag controversy.

Loyalists have been staging protests across the country to show their opposition to the decision to restrict the number of days the flag is flown over Belfast City Council.