Thousands of protesters during the G20 summit, police buy zone (Photo)

But protesters had no chance of arriving near the leaders of the United States, Russia, China and other world powers, who gathered for a meeting whose agenda was expected to be dominated by the US-Kina trade war.

Police, Coast Guard and border patrols surrounded an area of 12 square miles (5-shemen-mile) at the Costa Salguero Centre, where the summit is being held, while goods traffic on the La Plata River closed for the event.

The march, organised by a coalition of labour unions and rights groups, was held about 5km from the summit. Buenos Aires was largely closed in many areas. Public transportation was suspended and there were hundreds of transport lines to block and control traffic and crowds, tch broadcasts.

Friday was announced as a National Bank holiday, and Argentina's centre-right government suggested that people leave the city during the summit. These measures made it difficult for activists to march near the meeting area.

Protests are common at such major global gatherings, with different groups of demonstrators often finding common ground to protest what they see as neglected, marginalising the poor, for the rich world..