BUENOS AIRES (Reuters) - Thousands marched through Argentina’s capital on Wednesday to protest austerity measures under President Mauricio Macri, as a nationwide strike brought the airports of the recession-plagued country to a standstill and halted work at key grains ports.

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The strike, called by the country’s main unions, comes as center-right leader Macri tumbles in the polls ahead of presidential elections in October, his popularity with voters hurt by high inflation, job losses and a weak peso.

With transport links down and many schools, offices and banks closed, streets in central Buenos Aires were eerily quiet in the morning ahead of the march, sparked by the powerful CGT umbrella union.

Closely tied to the Peronist political opposition, the CGT is demanding the government back salary increases that match high inflation - prices are up more than 50 percent over the last year - and that reduce the tax burden borne by workers.

In a video posted online, the union said it had gone on strike to force change in government policy as “the economic and social situation was getting worse day by day and inflation was destroying the purchasing power of people’s wages.”

The marchers strode through the center of Buenos Aires, carrying flags and banners protesting Macri’s International Monetary Fund-backed economic reforms, which the government sees as key to cutting a steep fiscal deficit.

“Enough of Macri and the IMF,” some of the placards read.

“It’s tough to make those who have never wanted for anything to understand the needs of the people,” trucking union leader Hugo Moyano said at a press conference on Wednesday, referring to former businessman Macri’s personal wealth.

The protests also targeted rising service fees, the result of government efforts to cut the deficit under a financing deal with the International Monetary Fund. High fees have exacerbated poverty levels.

The economic crisis has hurt Macri’s re-election chances badly, with the recently announced Peronist pairing of Alberto Fernández and ex-President Cristina Fernández de Kirchner ahead of the president in polls.

On Wednesday flights from Argentina’s airports were shut down as a result of the strike, while grain exports stopped at the ports in Rosario, one of the most important agro-industrial regions in the world.

The effects of the stoppage were also be felt in the soccer world. The “Recopa” final, a South American cup-winners game due to be played between Argentina’s River Plate and Brazilian team Atlético Paranaense, was postponed until Thursday because of the protest.

A government estimate suggested the strike would cost the economy more than 40 billion pesos ($900 million).

“We are fed up with the stoppages. It is the fifth that this government has suffered,” security minister Patricia Bullrich told a local radio station on Wednesday.

($1 = 44.4200 Argentine pesos)