Two explosions hit Northern Ireland's second largest city of Londonderry on Thursday in what a police source said were believed to be attacks by dissident Irish nationalists.

No injuries were reported.

One blast hit a tourist information office in the centre of the city and a second explosion happened near a social services office, also in the city, a police spokesman said.

Coded telephone warnings were received before both attacks, the police source told Reuters.

Some Irish nationalists, who want the British province of Northern Ireland to be part of a united Ireland, have attacked government offices in recent months.

The office housing the organising committee for Londonderry's term as UK City of Culture in 2013 were hit by bomb attacks twice last year.

A 1998 peace agreement largely ended more than three decades of violence between mainly Catholic Irish nationalists and predominantly Protestant unionists who want the province to remain British.

However, dissident nationalists fight on with sporadic gun and bomb attacks, which have intensified in the past few years.

(Reporting by Ivan Little Editing by Louise Ireland and Conor Humphries)