The Greenpeace environmentalists, including a Briton and an Argentinian, are accused of obstructing police, illegally boarding the Vemamagna in Gibraltar harbour and of dangerous navigation during a January 20 protest.

Two Spanish journalists are charged with resisting arrest and threatening behaviour.

A Spaniard and a Portuguese are also among the Greenpeace activists on trial.

All six defendants entered not guilty pleas.

A total of 20 people, including 12 journalists, were arrested during the protest, but only six have been charged.

Speaking outside the court, Greenpeace spokesman Juan Lopez Uralde said: "We are confident we are innocent."

The Greenpeace activists unfurled banners with the logo "oil hazard" in English and Spanish after boarding the Vemamagna.

Their action came two months after the sinking of the single-hull tanker Prestige, which foundered last November off Spain's northwestern coast, causing an ecological disaster when thousands of tonnes of oil spilled from the vessel's hold.

Judicial sources said the trial would hear evidence from 28 witnesses and would likely last two weeks.

TERRA.WIRE