Argentine President Cristina Fernandez has described as "irresponsible" farmers blamed for fires that have left a blanket of smoke across Buenos Aires.
The fires from burning scrubland near the capital have disrupted air and road travel and smoke has spread across the River Plate to Montevideo, Uruguay.
The government accused the farmers of setting the fires off to clear pasture.
Farmers rejected the charge, saying it was designed to distract attention from a row over tax rises on farm exports.
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Smoke causes chaos in Buenos Aires
Roads, airports and ports have been closed and Buenos Aires residents, complaining of breathing difficulties and problems with their eyes, are closing their windows and staying indoors.
The smell of burning is everywhere, the BBC's Daniel Schweimler reports from the city.
Fire-fighters are battling to control the flames that have spread over thousands of hectares.
'Hand of man'
Argentine Interior Minister Florencio Randazzo said more than 300 fires had been detected.
Cattle farmers were "paying no heed to the consequences, just focusing on maximising profits", he said.
"We are facing a disaster caused by the hand of man," he said, warning farmers faced prosecution.
Argentine's left-wing government has been locked in a separate dispute with farmers over increases in export taxes on agricultural products.
Earlier this month, the farmers suspended a strike which had led to shortages, but gave the government until the end of the month to address their concerns.
Meanwhile, Buenos Aires residents are hoping for a change in the wind direction to clear the smoke which is making their lives a misery, our correspondent adds.
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