Mauritius and the Seychelles on Tuesday signed a pact to jointly manage a continental shelf in the Indian Ocean spanning 396,000 square kilometres in what was described as a pathbreaking accord.

The pact came after the two island nations obtained conjoint rights on the Mascarene Islands continental shelf in March last year. The treaty was signed during a visit by Seychelles President James Michel.

"It's a world first in that it's the first time that two island nations have reached an agreement on managing the continental shelf without calling a referee," said Joshua Brien, a Commonwealth official specialising in maritime frontiers.

The accord outlines the exploration and management of the seabed to pool out petrol and gas reserves and mineral deposits as well as living organisms.

A second treaty concerns the management of marine resources.

The treaties were signed by Mauritius Prime Minister Navin Ramgoolam in the presence of Commonwealth Deputy Secretary General Ransford Smith.