Police in Oslo have found a "bomb-like" device and are holding a suspect in custody.

"We are investigating and we have detained one suspect," the country's police force said in a tweet.

A large part of the city centre was cordoned off as police investigated further.

The device was later detonated in a controlled explosion.

Norwegian news site NRK said police spotted a suspicious man in the area, questioned him him and then found the device.

NRK quoted a police spokesman as saying that "it would appear that this is an object that does not have huge potential for injuries."

"I can not confirm [it is a bomb], but it is an object that is about 30 by 30 centimetres, that is to say that there is potential for damage in it, but it is of such a nature that we want the bomb squad to examine it,"police spokesman Svein Arild Jørundland told NRK.

The incident happened less than a mile from the government buildings that were damaged in a deadly bomb attack carried out by right wing extremist Anders Breivik in 2011. That bomb and a subsequent gun massacre killed a total of 77 people.

Eivind Flognfeldt, the owner of a nearby pub, told NRK that his staff had been asked to evacuate the premises.