Police fired tear gas and stun grenades at protesters in Ferguson, Missouri on Monday, after days of unrest sparked by the fatal shooting of an unarmed black teenager by a white policeman.
The police action came after hours of street protests that had been tense but mostly peaceful, Reuters witnesses said, adding there was also a projectile hurled from a crowd of protesters that shattered on the ground and erupted into flames.
Missouri's governor had lifted a curfew for the St. Louis suburb of Ferguson on Monday as National Guard troops were called out.
The National Guard deployment was the latest step by authorities to end the looting and burning of stores that have punctuated protests and stirred questions about race relations in the United States since the shooting death of Michael Brown, 18, on Aug. 9.
Governor Jay Nixon, who had declared a state of emergency for the town on Saturday and ordered the streets cleared for a curfew that ran from midnight to 5 am, said the National Guard would fall under the supervision of the Missouri Highway Patrol.
National Guard troops could be seen walking on the fringes of the gathering, keeping a distance from protesters.
President Barack Obama said he told the governor the use of the National Guard should be limited and urged healing, instead of violence. Attorney General Eric Holder will travel to Ferguson on Wednesday, Obama said.