CNN's Greg Lefevre reports. CNN's Rusty Dornin explains. Earlier, police in riot gear fired pepper spray to disperse protesters attempting to disrupt the opening session. Activists representing a rainbow of causes have vowed to shut down the city with acts of civil disobedience. Police acted when they failed to persuade demonstrators to clear an intersection at Seattle's Union Square, near the Convention Center where trade delegates are meeting.
Police report one arrest but no serious injuries following the clash.
The use of pepper spray creates a smoke-like fog that resembles tear gas, but police said they did not use tear gas. They also denied reports they used rubber bullets. Witnesses also reported seeing demonstrators hitting police officers and throwing what looked like wooden sticks at them. There was no immediate word on injuries from either side. The pepper spray succeeded in clearing the crowd, but other intersections around the city were still blocked by demonstrators trying to block access to the meeting's venue.