Image caption Two areas in Londonderry remain cordoned off

A huge security operation is taking place in Londonderry following two bomb attacks in the city on Thursday night.

The bombs exploded at the tourist centre on Foyle Street and on Strand Road, close to the DHSS office, within 10 minutes of each other.

Homes and businesses were evacuated by police and no-one was injured.

Police received a warning at 19:33 GMT. The first bomb went off on Foyle Street at 20:44 GMT and the second explosion occurred at 20:48 GMT.

They have described the attacks as "cowardly and callous".

The PSNI District Commander in Derry, Superintendent Stephen Martin, said the attacks were "cowardly and callous".

"Thankfully we are not dealing with mass casualties or worse this evening," he said.

Media playback is unsupported on your device Media caption The BBC's Mark Simpson said the bombs went off in what would have been a busy area of the city centre

"The reckless acts of those who planted these devices stand in stark contrast to those of the brave officers who entered these areas to evacuate local residents and businesses.

"The people in Derry do not want this disruption."

The extent of any damage to property is not yet known.

A number of elderly residents had to be moved from a residential home during the police operation.

One woman said she had been told there was a bomb at the bottom of the street.

"We heard one (bomb) go off. It was very loud," she said. "It was getting everybody out of the place where we live. But we all got out safely enough. They sent a bus for us and took us to this hotel."

SDLP Foyle MP Mark Durkan expressed anger at the explosions.

'Violent campaign'

"These attacks on people trying to bring things forward in this city are cowardly, destructive and totally unjustifiable," he said.

"I appeal to those responsible to cease their violent campaign and urge people with information about the perpetrators to pass any information they may have about these incidents onto the police urgently."

Sinn Fein MLA Martina Anderson condemned "the mindless actions of organisations that command miniscule support".

"We now have the opportunity to realise our goals and aspirations through peaceful and democratic methods, through persuasion and force of argument instead of force of arms," Ms Anderson said.

"Whatever organisation planted these bombs needs to come forward and explain how they believe that it has achieved anything other than disruption of older people who have had to be evacuated to a local hotel."

DUP MP Gregory Campbell said the people behind the bombings should realise they would not win.

"They're not going to defeat us if they bomb next week, next year or in 20 years time, they are not going to defeat the people of Londonderry," he said.

"And the UK City of Culture is going to come and we're going to enjoy it. That's going to happen no matter what they do."

Ulster Unionist leader Tom Elliott blamed dissident republicans for the attack.

"This type of fascism was part of our past. It has no place in our future."

The area remains cordoned off. Police have warned of considerable disruption to traffic on Thursday night and for much of Friday.

Motorists who had left vehicles at Foyleside shopping centre will be able to collect them on Friday, although management at the shopping centre say the police will tell them when vehicles can be released.

Meanwhile, Derry City Council office is expected to remain closed on Friday.

The city will be UK City of Culture in 2013 and last year dissidents attacked the office used by the organisers of the festivities.