(CNN) -- Six journalists were taken into custody while covering the protests in Ferguson, Missouri, on Monday and early Tuesday, aggravating what one press freedom group has called a "concerted, top-down effort to restrict the fundamental First Amendment rights of the public and the press."
The incidents bring the total number of journalists arrested during the mid-August protests to 11.
Other journalists reported being threatened with arrest and affected by tear-gas on Monday night. Authorities tried to restrict members of the news media to a designated area away from the protests, sometimes nicknamed a "press pen."
The latest arrests came on the same day that President Barack Obama reaffirmed his support for journalists on the ground in Ferguson. "Let me also be clear that our constitutional rights to speak freely, to assemble, and to report in the press must be vigilantly safeguarded, especially in moments like these," the President said at a Monday afternoon news conference.
A couple of hours later, Getty Images photographer Scott Olson was arrested. Getty, one of the main suppliers of photos to news outlets around the world, immediately condemned the police action.
Olson was released without charge after a few hours. Pancho Bernasconi, Getty's vice president for news, said in a statement that Olson later told him: "I want to be able to do my job as a member of the media and not be arrested for just doing my job."
Kerry Picket, a reporter for the conservative website Breitbart News, was arrested around the same time as Olson. She was held for "several hours," the website said.
"Picket was released when it was discovered that the trooper misunderstood directions from his superiors and was told to not allow vehicle traffic through but to allow foot traffic through. Both the arresting officer and his lieutenant apologized to Picket," Breitbart News added.
The first arrests of journalists came last Wednesday when Ryan Reilly of The Huffington Post and Wesley Lowery of The Washington Post were arrested inside a McDonald's in Ferguson. They were released 45 minutes later without being charged. Three other reporters were detained for a few minutes on Sunday night.
Last week, a number of press advocacy groups decried the initial spate of arrests. The American Society of News Editors called it a "top-down effort to restrict" First Amendment rights; the group's president, David Boardman said "the police have made conscious decisions to restrict information and images coming from Ferguson."
Of course, Boardman added, "For every reporter they arrest, every image they block, every citizen they censor, another will still write, photograph and speak."
Three journalists from German newspapers were also taken into custody on Monday evening. Two of them, Ansgar Graw and Frank Herrmann of the newspaper Die Welt, were detained for three hours and then released without any charges.
"This was a very new experience," Graw wrote, according to an English-language translation of his German-language account. "I've been in several conflict zones: I was in the civil war regions in Georgia, the Gaza strip, illegally visited the Kaliningrad region when travel to the Soviet Union was still strictly prohibited for westerners, I've been in Iraq, Vietnam and in China, I've met Cuba dissidents. But to be arrested and yelled at and be rudely treated by police? For that I had to travel to Ferguson and St. Louis in the United States of America."
Another German reporter, Lukas Hermsmeier of the newspaper Bild, was arrested early Tuesday morning, along with Ryan Devereaux, a reporter for The Intercept, an online news start-up best known for covering NSA mass surveillance.
Hermsmeier and Devereaux met Monday when they were seated in the same row on a flight to Missouri.
John Cook, the editor in chief of The Intercept, said it was unknown why Devereaux was detained.
"But needless to say, it's an outrage that he was stopped and handcuffed by police in the course of lawfully doing his job on the streets of Ferguson," Cook said.
Devereaux's last Twitter message before the arrest came around 2 a.m. ET Tuesday. "So much smoke in this neighborhood right now, seems like the police succeeded in clearing out the rest of the demonstrators," he wrote.
He said around 9:45 a.m. that he had been released. "Out of jail. Too many still in there," he wrote.
Missouri Highway Patrol Capt. Ron Johnson said at a news conference early Tuesday morning that 31 people had been arrested amid Monday night's protests.
When asked about the journalists, he said, "In the midst of chaos, when officers are running around, we're not sure who's a journalist and who's not. And yes, if I see somebody with a $50,000 camera on their shoulder, I'm pretty sure. But some journalists are walking around and all you have is a cell phone because you're from a small media outlet. Some of you may just have a camera around your neck."
"So yes, we are -- we may take some of you into custody," Johnson said. "But when we do take you to custody, when we've found out you're a journalist, we have taken the proper action."