Divers have salvaged what is believed to be the world's oldest preserved beer from a 200-year-old shipwreck, the government of the semi-autonomous Aland Islands in the Baltic Sea between Finland and Sweden said Friday.

'At least three, four beer bottles were salvaged,' permanent secretary Rainer Juslin of the local government of Aland told DPA.

The beer was discovered Wednesday when a bottle broke during the final salvage operation, revealing what till than had been the bottle's unknown contents.

A team of divers earlier this summer discovered dozens of champagne bottles on the wreck in the archipelago of the Swedish-speaking islands that are part of Finland.

Tests of the champagne have suggested it had retained its qualities.

The consistent water temperature and light levels at some 50 metres depth were factors that benefited the storage of the bottles. In addition, seawater did not seep in due to the pressure in the bottles.

Juslin said some 70 champagne bottles have been salvaged. However, experts have advised the Aland authorities not to disclose how many of the bottles are unspoiled since that could affect a possible auction price.

Each bottle was believed to be worth tens of thousand dollars, but the value of the beer has not been estimated.

The sale could possibly provide funds for marine archealogy off the islands, Juslin said, but no decision has been made.

A stamp on a bottle cork helped experts determine that it was made by a champagne house founded in 1802 and sold in 1829, Juslin said.

Experts are still trying to determine the identity of the ship.

Other artefacts salvaged from the wreck like a stamped china plate also support the theory it dates from the early 1800s, Juslin added.

Juslin said as far as the Aland government had been able to determine, the oldest known preserved beer was from England and dated from 1869.