Argentinians protesting against the building of a paper mill in neighbouring Uruguay cut road links between the two countries on Friday.
The mill is being built by a Finnish company close to the Uruguay river
The demonstration was launched after the World Bank indicated it would go ahead with funding for the project.
About 300 people blocked roads leading to a bridge across the Uruguay river in the town of Gualeguaychu, 240km north of Argentina's capital Buenos Aires.
Locals fear the $1.7bn project could cause pollution and harm tourism.
Protests against the plant in the Uruguayan town of Fray Bentos also closed a cross-border bridge upstream near the Argentinian town of Colon.
"No one in Gualeguaychu is going to tolerate that the mills belch out smoke that could hurt our children," protester Daniel Perez told Reuters.
Argentina's objections to the pulp mill have risked a diplomatic rift between the two countries after Buenos Aires took the issue to the International Court of Justice, the Hague tribunal which arbitrates cross-border issues between countries.
The court ruled in July that the project could go ahead, and on Wednesday the World Bank announced that the plant met its environmental standards.
The announcement paves the way for the World Bank's International Finance Corporation to approve $400m of loans for the project, although a final decision on the loans is yet to be made.
EcoMetrix, the Canadian company that conducted the World Bank environmental impact study, wrote that emissions from the mill would be "well below" accepted levels and that local industries were unlikely to face long-term problems.
The project has aroused strong passions
Argentina's environment secretary Romina Picolotti dismissed the World Bank report this week but also attacked the protesters, saying they could harm the government's attempts to resolve the issue diplomatically.
Uruguay claims an earlier round of demonstrations over the plant had caused the country $200m in lost tourism and trade.
The wave of protests against the project have already caused Ence, the Spanish company that was developing one of two pulp mills for the site, to relocate its project elsewhere in Uruguay.
But the mill being built by Finnish company Botnia is still going ahead.