Police and protesters clashed in Pittsburgh, where the world's richest nations gathered as environmental and anarchist groups massed on the streets.
Witnesses said cops fired tear gas at members of a group calling itself the Pittsburgh G-20 Resistance Project. The group had announced its intention to mount an unauthorized march, and some observers feared it could boil over as has happened at past meetings of powerful world leaders. A 40,000-strong crowd of anarchists at the 1999 World Trade Organization meeting in Seattle fought running battles with police and vandalized buildings.
"What I fear at the march is over-reaction by the authorities and over-reaction by some of the younger protesters," said Michael Healey, a civil rights lawyer representing 14 Greenpeace activists who were arrested in Pittsburgh on Wednesday after scaling a bridge to hang a sign warning of environmental doom. "It's a toxic mix."
Several small businesses planned to shut during the two-day meeting, and workmen were boarding over shop windows in the downtown business district. Some protesters felt threatened by the very steps the city was taking to deal with them.
"The city has bought a thousand cannisters of tear gas. That's something people are concerned about, like what to do if they're gassed," said Noah Williams, a spokesman for the Pittsburgh G-20 Resistance Project.