Tear gas is fired at G20 protesters
US police at the G20 summit in Pittsburgh have fired tear gas during a game of cat and mouse with anti-capitalist protesters.
As the leaders of the world's richest nations gathered ahead of crucial talks, scores of anarchists were involved in a tense stand-off with heavily armed security forces.
Demonstrators had earlier gathered in a park on the outskirts of the US city with the intention of marching to the site of the summit.
But they were repeatedly thwarted in their attempts to break through police lines.
Despite stones being thrown at one stage and at least one arrest there was no clear sign of mass violence or confrontation.
But protesters at one flashpoint reported the use of tear gas to disperse the crowds.
About 90 minutes into the stand-off, demonstrators had not managed to get any further than a few blocks.
