BUENOS AIRES, Argentina (AFP) -- Argentines expressed outrage yesterday that Uruguay was not slapped with sanctions or penalties after being found in violation of an international treaty by polluting a river the countries share.

"This is a bitter pill we have to swallow," said Sergio Uribarri, governor of the Argentine border province of Entre Rios, reacting to the ruling by the International Court of Justice in The Hague.

"We know that the court ruled in our favour on the basic question. But it's still important to correct the problems" highlighted by the court's verdict, Uribarri said.

The ruling led more than 2,000 environmental rights activists to take to the streets of Buenos Aires.

"This factory is illegal and it's a polluter," said one of them, Lalo Moreyra, who added that Argentines "will never accept that the plant be allowed to remain open".

The International Court of Justice in the Hague yesterday ruled that "Uruguay breached its procedural obligations" by not informing Argentina about the paper-processing plant on the River Uruguay.

Nevertheless, the court chose not to hold Montevideo responsible for polluting the river.

Argentina accused its neighbour of having reneged on the treaty when it authorised the $1-billion (euro740-million) Botnia mill, which Buenos Aires claimed has caused "irreversible" environmental damage to a densely populated area used for fishing, leisure and tourism.

The mill is owned by Finnish firm Botnia, which started operating on the Uruguayan bank of the river near the town of Fray Bentos in November 2007.

The court ruled that by not informing Argentina of the plans before authorising the Botnia mill, Uruguay "failed to comply with the obligation imposed on it" by a 1975 bilateral treaty with Argentina.

Uruguay's Foreign Minister Luis Almagro said in a statement that he was seeking a meeting of leaders from both countries to try to find a resolution of the dispute and discuss the international court ruling.