LIMA (AFP) - Peru on Saturday (Jan 22) declared an "environmental emergency" along a stretch of coast hit by an oil spill caused by freak waves from a volcanic eruption in the South Pacific.

With the 90-day decree, the government said it plans "sustainable management" of 21 beaches tarred by 6,000 barrels of oil that spilled from a tanker ship unloading at a refinery last Saturday.

That accident followed the stunningly powerful eruption of an undersea volcano near the nation of Tonga, unleashing tsunami waves around the Pacific and as far away as the United States.

In Peru the oil spill near Lima has fouled beaches, killed birds and harmed the fishing and tourism industries.

The government is demanding payment of damages from the Spanish energy giant which owns the refinery.

The environment ministry said 174 hectares - equivalent to 270 football fields - of sea, beaches and natural reserves were affected by the spill.

Crews are working to clean up the spill.

In declaring the emergency Saturday, the environment ministry said: "the spill amounts to a sudden event of significant impact on the coastal marine ecosystem, which has major biological diversity." It said that over the short term Repsol is responsible for emergency clean up operations.

Its refinery is in the town of Ventanilla near Lima.

Repsol has said the spill occurred because of freak waves caused by the eruption in the Pacific.

The company is arguing that it is not responsible for the spill, however, because it says the government gave no warning that there might be rough waters from that undersea blast half way across the world.

Last week fishermen and other local people who live off the sea and tourism staged protests over the sudden loss of their livelihood.