By Scott Malone

FERGUSON, Mo. (Reuters) - Four white men carrying military-style rifles and sidearms added a disquieting element to riot-torn Ferguson, Missouri, when they began patrolling the streets before dawn on Tuesday, which police quickly labeled "inflammatory."

The men said they were part of a group called "Oath Keepers," which describes itself as a non-partisan association of current and former U.S. soldiers, police and first responders who aim to protect the U.S. Constitution. They told reporters on the street that they were in Ferguson to protect a media organization.

The men attracted immediate attention in the mostly black neighborhood, which exploded into violence on Sunday night as protesters marked the one-year anniversary of the killing of an unarmed black teen by police.

The Southern Poverty Law Center, a non-profit civil rights organization, has described the "Oath Keepers" as a "fiercely anti-government, militaristic group," and St. Louis County Police Chief Jon Belmar condemned their appearance in Ferguson.

"Their presence was both unnecessary and inflammatory," he said, adding that police would work with county prosecutors to see if the men had broken any laws.

The men told reporters they were licensed to carry firearms. A voter-backed 2014 amendment to the state constitution cleared the way for open carrying of licensed firearms, so long as they are not used in a threatening manner, legal experts said.

"There is no exception for a state of emergency for these laws not to apply," said Marcia McCormick, a professor of law at St. Louis University Law School.

State law prohibits brandishing a weapon in an "angry or threatening manner," McCormick said, but that standard is subject to interpretation.

"Clearly the people who are carrying these weapons are trying to send a message that some might see as threatening but it's probably not a violation of the statute," McCormick said.

Many in the crowd questioned the wisdom of openly carrying such heavy weapons into an emotionally charged situation.

"You’re going to bring some uncommissioned citizens, white citizens, into a black community like this? It's disrespectful," said Talal Ahmad, 30, who is black and was a fixture at last year's protests.

"Here, in a black neighborhood, we’re already living in a state of terror," Ahmad said.

'WE NEEDED TO BE PREPARED'

The group, led by a man identified only as John, wore bulletproof vests and carried their rifles with barrels pointed downward. They said they were in Ferguson to protect a journalist from the conservative "Infowars.com" website.

"There were problems here, there were people who got hurt. We needed to be prepared for that," said John.

Members of the group had patrolled the streets of Ferguson for a time in November, after riots erupted when a grand jury found that a white police officer had broken no laws when he shot dead 18-year-old Michael Brown.

Sunday night's protests were punctuated by gunfire, and police shot and critically wounded a man accused of firing on police.

An Infowars representative acknowledged by telephone that the Oath Keeper's had a presence in Ferguson but said it had not asked them for security.

"We happen to be in some of the same circumstances as they are on occasion and ideologically we may share the same views," said the representative, who asked not to be named citing security concerns. "They are there of their own volition and secondarily they are there to protect anyone who is innocent. Of course, we fall under that because our reporters are reporting."

Protests on Monday were less chaotic than they had been on Sunday. Twenty-two people were arrested in nighttime skirmishes with police during which protesters threw rocks and bottles at officers on the block where the Oath Keepers appeared. Another 63 people were arrested earlier in the day after blocking a highway.

(Reporting by Scott Malone; Additional reporting by Fiona Ortiz in Chicago; Editing by Toni Reinhold)