The European Union has won the Nobel Peace Prize for its historic role in uniting the continent.

The award is meant as a morale boost for the bloc as it struggles to resolve its debt crisis.

The EU has been a key in transforming Europe "from a continent of wars to a continent of peace," Committee chairman Thorbjoern Jagland said as he announced the award in Oslo.

"This is a message to Europe to do everything they can to secure what they've achieved and move forward," Jagland said.

He added it was a reminder of what would be lost "if the union is allowed to collapse".

Jagland praised the 27-nation EU for rebuilding after World War Two and for its role in spreading stability after the 1989 fall of the Berlin Wall. The prize, worth €925,000, will be presented in Oslo on December 10.

The decision by the five-member panel, led by Jagland who is also Secretary-General of the Council of Europe, was unanimous.

The EU won from a field of 231 candidates including Russian dissidents and religious leaders working for Muslim-Christian reconciliation.

But the EU is mired in crisis with strains on the euro, the common currency shared by 17 nations and the prize was a surprise given the EU's current woes.

Many Norwegians are also bitterly opposed to the EU, seeing it as a threat to the sovereignty of nation states.

"I find this absurd," the leader of Norway's anti-EU membership organisation Heming Olaussen told NRK. "In Latin America and other parts of the world they will view this quite differently than they will from Brussels. The union is a trade bloc that contributes to keeping many countries in poverty," he said.

Norway, the home of the peace prize, has voted "no" twice to joining the EU, in 1972 and 1994. The country has prospered outside the EU, partly thanks to huge oil and gas resources.

The five-member Nobel committee is appointed by parliament, where parties are deeply split over EU membership. Jagland has long favoured EU membership.

The European Union's top official Herman Van Rompuy said the awarding of the Nobel Peace Prize recognised the bloc's role as the 'biggest peacemaker in history'.

"We are all very proud that the efforts of the EU for keeping the peace in Europe are rewarded," he said during a visit to Helsinki today after as the Norwegian Nobel Committee announced the award.

"Europe got through two civil wars in the 20th century and we have established peace thanks to the European Union. So the European Union is the biggest peacemaker in history," he said.