FERGUSON, Mo. — The National Guard arrived in Ferguson but kept its distance from the streets where protesters clashed again with police, as clouds of tear gas and smoke hung over the St. Louis suburb where Michael Brown was fatally shot by a police officer.

Protesters filled the streets after nightfall Monday, and officers trying to enforce tighter restrictions at times used bullhorns to order them to disperse. Police deployed noisemakers and armored vehicles to push demonstrators back. Officers fired tear gas and flash grenades.

Capt. Ron Johnson of the Missouri Highway Patrol, who is in charge of security in Ferguson, said bottles and Molotov cocktails were thrown from the crowd and that some officers had come under heavy gunfire. At least two people were shot and 31 were arrested, he said. He did not have condition updates on those who were shot. Johnson said four officers were injured by rocks or bottles.

Demonstrators no longer faced the neighborhood’s midnight-to-5 a.m. curfew, but police told protesters that they could not assemble in a single spot and had to keep moving. After the streets had been mostly cleared, authorities ordered reporters to leave as well, citing the risk from gunfire that had been reported.

A photographer for the Getty photo agency was arrested while covering the demonstrations and later released. Two German reporters were arrested and detained for three hours. Conservative German daily Die Welt said correspondent Ansgar Graw and reporter Frank Herrmann, who writes for German regional papers, were arrested after allegedly failing to follow police instructions to vacate an empty street. They said they followed police orders.