Law enforcement personnel in the U.S. state of Missouri interfered with two German journalists who went to the town of Ferguson to cover disturbances sparked by a fatal police shooting, a representative of Reporters Without Borders said here Tuesday.

The arrests of reporters Ansgar Graw and Frank Herrmann for not following police instructions are "completely unacceptable," the spokeswoman for the German branch of Reporters Without Borders said.

"We demand that reporters are allowed to do their jobs in Ferguson without having to be afraid of being arrested by the police, or even shot at," Astrid Frohloff said in a statement released in Berlin.

Graw, a correspondent with national daily Die Welt, and Herrmann, whose work appears in regional newspapers, were held for three hours at the St. Louis County jail after they allegedly disobeyed police orders to keep moving.

The reporters were standing on an empty street to photograph a gas station that had been looted and set on fire.

Authorities confiscated their photos before releasing the two men.

Lukas Hermsmeier, who has been reporting from Ferguson for German tabloid Bild, said Tuesday that he was also arrested and taken to the county jail.

Two men were wounded by gunshots and 31 other people were arrested in Ferguson overnight during protests over the Aug. 9 shooting death of an unarmed African-American teenager by a white police officer, Missouri Highway Patrol Capt. Ron Johnson said.

A peaceful protest turned violent as night set in, despite the deployment of the National Guard in the St. Louis suburb. EFE