Protesters at the rally held signs reading "Don't insult Malays and Islam" and "#najibstays". Some were eventually dispersed by riot police outside Chinatown, where many Chinese businesses are located.
There, witnesses said, they hurled racial abuse against ethnic Chinese and threatened a repeat of 1969, when ethnic rioting killed hundreds of people, mostly Chinese. Communal tension has simmered in the succeeding decades, and some fear that racially volatile mass gatherings like the Sept. 16 rally could spiral into violence.
"It's not a threat," Ali Rustam, the head of the Malay group, said of the rally in an interview. "It's a reminder: Don't play with fire. Don't insult the Malays too much."
Malays make up about 60 percent of Malaysia's 30 million people and Chinese about 25 percent. There is also a sizeable Indian minority.