At least 48 people were arrested in Louisiana Sunday after an unplanned peaceful protest against last week’s police killing of a 37-year-old Alton Sterling ended up with some tense moments.

According to WAFB-TV, a street in downtown Baton Rouge was closed after a group held an “unlawful protest” following a peace march at the state capitol. Police said they believe the second protest was executed by an out-of-state group.

"Protesters were attempting to get onto and block the interstate," Baton Rouge police Cpl. Don Coppola told the station. "We were able to stop them before they were able to achieve that."

The secondary protest started at around 6 p.m. and lasted until about 8:30 p.m. As they were trying to get onto the highway, police blocked the ramps to Interstate 110 north and south. The protesters were told to leave the area.

The protest leaders urged demonstrators to remain peaceful, but as the march wore on some protesters started to throw rocks toward officers. Police said no one was injured.

Coppola blamed some violence and the large number of arrests – which could top over 150 for the weekend – on outside agitators. One officer lost teeth to a projectile thrown outside police headquarters, and police also confiscated three rifles, three shotguns and two pistols during that protest, he wrote in an email to the Associated Press.

Most of those detained faced a simple charged of obstructing a highway, sheriff’s spokeswoman Casey Rayborn Hicks said.

Earlier, some police officers were seen in riot gear and officials said they were prepared to use a chemical agent on protesters if needed. They began to move the crowd out of the area at around 7:30 p.m.

Gov. John Bel Edwards said he's "very proud" of the Louisiana law enforcement response to protests over the fatal shooting of a black man by white police officers in the city.

Flanked by law enforcement leaders, Edwards said he doesn't believe officers have been overly aggressive by using riot gear to push protesters off a highway.

"The police tactics in response have been very moderate. I'm very proud of that," said the Democratic governor, who comes from a family of sheriffs.

Tensions between black citizens and police have risen palpably over the past week or so amid police shootings of African-American men in Minnesota and Louisiana and the gunning down of five white police officers by a black suspect in Dallas in apparent retaliation.

The tumult reached well beyond Louisiana. In Minnesota, authorities said 21 law enforcement officers were hurt and about 100 people were arrested late Saturday and early Sunday during clashes in the state capital over the police killing of Philando Castile.

There was very little violence by comparison in Baton Rouge.

"I can assure everyone we are hearing the protesters," the governor said. "We are listening to their voices. But I'm especially gratified that our citizens here in Louisiana, to a very large degree, have decided to protest in a constructive and peaceful manner."

Edwards said hundreds have marched around the city, with only one injury to an officer and mostly misdemeanor arrests. Protesting peacefully is the best way to honor those killed, he said, adding that authorities won't allow people "to incite hate and violence."

"I want to be clear that will not be tolerated. We don't operate like that in Louisiana," he said.

The list of those arrested released by the sheriff's office included two homeless people, and 18 are from out of state, including prominent Black Lives Matter activist Deray Mckesson. The vast majority of the Louisiana residents were from the Baton Rouge and New Orleans areas.

The Associated Press contributed to this report.

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