Hundreds of protesters broke through police lines and came close to storming into the WTO's meeting venue Saturday, but security forces scattered the crowd with tear gas.
It was the worst street violence Hong Kong has experienced in decades, and police quickly locked the doors to the convention center, where trade ministers from around the world were in the final hours of a six-day negotiation.
A government statement said 70 people _ including 10 police _ were sent to hospitals for treatment and three of them were admitted.
Police Commissioner Dick Lee said police have detained 900 people and were determining whether to formally arrest them. "If necessary we will make arrests. We will not let them go easily," he said.
Elizabeth Tang, spokeswoman for the group organizing the marches, said she would not rule out calling off Sunday's march, which was to be the biggest one during the &to=http://english.pravda.ru/mailbox/22/101/399/16613_WTO.html' target=_blank>World Trade Organization meeting.
"We are still discussing it with members. Some members may not agree to marching," said Tang of the Hong Kong People's Alliance on WTO.
Security forces spent much of the afternoon fighting running street battles with the protesters, who included South Korean farmers, Southeast Asian groups and activists from Europe and America.