Two FBI agents have been shot and wounded at a house in north St. Louis County, near the protests in Ferguson over the killing of African-American teenager Michael Brown.

It was not immediately clear if the incident was related to the unrest in Ferguson, which is also in St. Louis County. CBS News reported that the gunfire took place five miles outside of the flashpoint town.

The agents went to the house to deal with a person barricaded inside the residence. Both suffered non-life threatening injuries, according to Reuters.

The FBI has not responded to requests for comment.

A dozen American cities have witnessed protests over the decision not to indict policeman Darren Wilson for killing Brown.

Riots broke out in Ferguson - where police made 44 arrests - Oakland and California. Over 2,200 National Guard soldiers were dispatched to assist police in maintaining order in Ferguson, where 44 arrests were made overnight.

Wilson has given an exclusive interview to ABC in which he said that he has a "clean conscience" over the shooting.

"The reason I have a clean conscience is because I know I did my job right," he said.