Scuffles broke out between police and farmers on a motorway
Farmers in Argentina have launched their fourth strike in as many months in a heated protest against tax increases on food exports.
Argentine riot police broke up a road blockade by protesting truckers and farmers on a main road near the border with Uruguay on Saturday.
A focus of the farmers' anger is an increase in the export tax on soya, which earned $13bn (£6.6bn) in 2007.
Argentina is one of the world's top exporters of wheat, soya and beef.
Riot police moved in to clear Route 14, a major road link with Brazil.
Nearly 20 protesters were temporarily detained, among them the leader of the local farmers' association, Alfredo de Angeli.
Other highways were being blocked by angry hauliers whose livelihood has been damaged by the ongoing tax dispute.
The lorry drivers' protest has led to fuel shortages and is threatening food stocks in parts of Argentina.
Leading activists said the latest strike would continue until Wednesday.
Argentina's President Cristina Fernandez de Kirchner last week defended her government's decision to impose higher export taxes.
She said the additional money raised would be spent on tackling poverty by building more housing, hospitals and roads.
Last Monday, the farmers had suspended the protests in the hope of returning to the negotiations with the government.