GREENPEACE activists clashed yesterday with a ship undertaking exploratory tests in the Atlantic.

Ten activists in three inflatable boats buzzed the survey ship Pacific Horizon and forced it to abandon the seismic tests for oil giant Texaco about 180 miles north-east of Rockall.

Oil company officials claimed later that the environmentalists steered into the path of the ship and threatened to jump into the sea near a large array of explosive devices being towed by the vessel.

Texaco condemmed the stunt and accused Greenpeace of putting its own people as well as the crew of the survey ship at risk. But Greenpeace warned yesterday's events were merely its opening shot of direct action to block the first phase of oil exploration in the area.

The environmental group's ship approached the Pacific Horizon before Ipm and asked the crew to stop what they were doing.

The array with the guns and recorders was already being trailed behind it.

When the captain refused the three fast inflatables were launched with a radio warning that activists would put themselves in danger and take to the water close to them if the air gun-type devices and recording equipment used as part of the testing were fired.

The devices cause loud explosions reaching 250 decibels to survey the rock formation of the ocean bed.

"Soon afterwards the captain of the Pacific Horizon said it would not carry out the seismic testing while Greenpeace inflatables remained near its 8 km long testing array," said Greenpeace last night.

"Three inflatables have continued to follow the testing ship to prevent it beginning its tests again."

A Texaco spokesman said the company regretted the actions of Greenpeace in hounding the survey ship.

"Activities such as this are unsafe and put the activists and the crew of the Pacific Horizon at considerable risk.

"They do nothing to address the real issues surrounding the safe and environmentally sound development of the UK's oil and gas resource."

Greenpeace opposes oil developments on the grounds of climatic change.

It argues that there is already four times more fossil fuels in reserve than can ever be burnt without causing irreparable damage to the climate.

Speaking from the mv Greenpeace, campaign director Chris Rose attacked Prime Minister Tony Blair for sanctioning the continuing explorations while saying in New York at the weekend that emissions of carbon dioxide from fossil fuels have to be radically reduced.

"It is not just hypocritical to do so, it is incredible. The stupidity of it defies belief," said Mr Rose.