At least 17 people are confirmed dead after two attacks in Norway.

Seven people are now known to have died in the massive bomb blast that struck Oslo this afternoon.

At least ten more have died in a related attack on the island of Utoeya with a senior police officer saying explosives have also been found there.

The bombing in the Norwegian capital took place shortly after 3.30pm local time (2.30pm Irish) and destroyed an area of the city which houses the Prime Minister's office and many government ministries.

Reports of a shooting at a youth rally being held by the Norwegian Labour Party in Utoeya emerged shortly afterwards.

Police have said at least ten people have died in the shooting, with reports suggesting it was carried out by a man dressed as a police officer.

A 32-year-old man was arrested at the scene and the country's justice minister has since said that he is Norwegian.

Police confirmed the two attacks were related and said they expected the death toll from the island to rise.

An earlier witness report had suggested that at least 20 people had been killed in Utoeya.

Prime Minister Jens Stoltenberg's party was holding a yearly gathering for youth members in Utoeya with 700 reported to have been in attendance.

The Prime Minister was due to give a speech at the meeting tomorrow. Former Prime Minister Gro Harlem Brundtland was due to attend the meeting today.

In Oslo, the office of the prime minister was at the heart of the area devastated by the bomb blast.

The blast blew out most windows on the 17-storey building housing Stoltenberg's office as well as government ministries.

Prime Minister Stoltenberg is reported to be safe, according to local media.

A Reuters correspondent in the area said the streets had been fairly quiet on a Friday afternoon in mid-summer, with many Oslo residents on holidays or away on weekend breaks.

The tangled wreckage of a car outside one building - as well as the damage to the surrounding structures - appeared to be consistent with reports of a car bomb.

The Department of Foreign Affairs says it has no reports of any Irish people affected so far.

Up to 300 Irish citizens are resident in Oslo but the department says it would not have figures on the number of tourists there at the moment.

All staff in the Irish embassy, which is located close to the scene of the bombing, are said to be safe and well.

The Tánaiste and Minister for Foreign Affairs Eamon Gilmore said he has sent a message to the Norwegian prime minister on behalf of the Irish Government.

In the message he expressed Ireland's solidarity with Norway and conveyed sympathy in respect of the deaths and injuries that have occoured.

President Mary McAleese also extended her condolences to Norway's King Harald and the Norwegian people.