The suspect charged with carrying out a massacre at a youth camp in Norway and a bombing in the capital, Oslo, which claimed the lives of at least 93 people, has said he acted alone.

Anders Behring Breivik, 32, admitted to carrying out both attacks, which he described as "gruesome but necessary".

"He says that he was alone but the police must verify everything that he said. Some of the witness statements from the island have made us unsure of whether there was one or more shooters," police chief Sveinung Sponheim said at a press conference, as cited by BBC.

He said police were not looking for anyone else at the moment - though they had not ruled out that the suspect might have had help.

Breivik had co-operated during his interrogation and there had been a "good" dialogue.

He has been charged over both attacks, and is due to appear in court on Monday.

Under Norwegian law the maximum time Breivik could face in prison is 21 years.

The death toll from the terrorist attacks is expected to rise. At least four people from the island camp shooting are yet to be found; it is thought some may have drowned after swimming out into the lake to escape the hail of bullets.

In Oslo police said more bodies and body parts were in buildings damaged by the bomb but still too unstable to search