Leading dignitaries have attended the official opening of a 'doomsday' seed vault built 130m (426ft) inside a mountain on a remote Arctic island.

Norwegian Prime Minister Jen Stoltenberg and Nobel Prize winner Wangari Maathai placed the first seeds in the depository during the ceremony.

The vault, designed to withstand all natural and human disaster, will house samples of all known food crops.

The Svalbard Global Seed Vault took 12 months and cost £5m to construct.

During the ceremony, Mr Stoltenberg unlocked the vault before being joined by environmental campaigner Ms Maathai to place the first consignment of seeds in the -18C (0F) freezer.

Reporter's log: Inside story

European Commission President Jose Manuel Barroso was among the 300 guests to attend the event.

"With climate change and other forces threatening the diversity of life that sustains our planet, Norway is proud to be playing a central role in creating a facility capable of protecting what are not just seeds, but the fundamental building blocks of human civilisation," said Mr Stoltenberg.

When full, the vault will hold 4.5m samples - an estimated two billion seeds - from more than 100 countries around the world.

'Fail-safe' facility

The collection and its maintenance is being organised by the Global Crop Diversity Trust, which has responsibility of ensuring the "conservation of crop diversity in perpetuity".

Map showing location of Svalbard (Image: BBC)

"Crop diversity will soon prove to be our most potent and indispensable resource for addressing climate change, water and energy supply constraints, and for meeting the food needs of a growing population," predicted Cary Fowler, the Trust's executive director.

The vault consists of three secure rooms at the end of a 125m (410ft) tunnel, and four sets of locked doors.

Dr Fowler said the role of the facility was not to replace national seed banks, but to act as insurance by storing duplicates of seeds from national collections.

If seeds are lost, for example as a result of a natural disaster, the collection can be re-established by using samples stored at Svalbard.

The site, 1,000km (621 miles) north of mainland Norway, was chosen because it was geologically stable, remote, and the surrounding permafrost would act as natural refrigeration to keep the facility at the temperature needed to preserve the seeds.