Argentina ? Striking farmers built new highway blockades around Argentina’s agricultural heartland Wednesday in a standoff with the president over tax increases on major export crops.

The nationwide farm and ranch strike headed into a third week, all but paralyzing one of the leading world exporters of soybeans, beef and wheat. There were no reports of major violence despite tension and fisticuffs at one barricade and huge traffic jams elsewhere.

Demonstrators held a second straight night of noisy pot-banging protests late Wednesday in Buenos Aires, rallying in the hundreds outside the downtown Government House and the suburban presidential residence. The downtown demonstration melted away quickly after a similar-size crowd of counter-protesters arrived waving flags in support of President Cristina Fernandez.

The strike by farmers against the government decree, which raises taxes on soybean exports from 35 percent to 45 percent and slaps new taxes on other farm exports, has led to shortages of beef, milk, cooking oil and other products on supermarket shelves in Argentina.