Thousands of Irish farmers are protesting against the EU’s trade deal with the South American bloc Mercosur, a day after EU states approved the treaty despite opposition from Ireland and France.

Tractors streamed into the roads of Athlone, in central Ireland, for the demonstration, displaying signs bearing the slogan “Stop EU-Mercosur” and the EU flag emblazoned with the words “sell out”.

The protests followed similar actions on Friday in Poland, France and Belgium as the EU gave the green light to the trade deal, which has been welcomed by business groups but heavily criticised by European farmers.

The accord, more than 25 years in the making, would create one of the world’s largest free-trade areas, boosting commerce between the 27-nation EU and the Mercosur bloc comprising Brazil, Paraguay, Argentina and Uruguay.

Major Mercosur exports to the EU include agricultural products and minerals, while the EU would export machinery, chemicals and pharmaceuticals with lowered tariffs applied.

But many European farmers fear their livelihoods will be undercut by a flow of cheaper goods from agricultural giant Brazil and its neighbours, prompting Ireland, France, Poland, Hungary and Austria to vote against the accord.

The agreement is widely opposed by Irish farmers over fears it will result in an influx of an extra 99,000 tonnes of cheap beef from South America, disrupting Irish agriculture.

The Irish Farmers’ Association (IFA), Ireland’s main farmers’ lobby group, called the result very disappointing, and said it would renew focus on securing a majority against the deal in the European parliament.

“We expect Irish MEPs to stand behind the farming community and reject the Mercosur deal,” said the IFA president, Francie Gorman, in a statement.

Earlier this week the Irish taoiseach (prime minister), Micheál Martin, expressed concern that Mercosur beef may not be produced to the EU’s strict environmental standards, saying people had to be confident that standards and obligations set for Irish farmers would not be undermined by imports with less stringent regulations.

At the Saturday protest, farmers carried signs calling for an “Irexit” and accusing the Latin American bloc’s beef exports of not following the same standards.

The Mercosur deal will also need to be agreed by a majority of MEPs in the European assembly in the coming months, where voting coalitions have become more volatile and unpredictable.