Two FBI officers shot at barricaded house in St Louis following a second night of unrest over Michael Brown shooting grand jury verdict

The FBI has said the incident 'is not directly related to the Ferguson protests'

Two FBI officers have been shot while responding to a person barricaded inside a house in St Louis, police have said (AFP/Getty)

Two FBI officers have been shot while responding to a person barricaded inside a house in St Louis, police have said.

St Louis County police spokesman Officer Shawn McGuire said the agents were shot early on Wednesday morning, roughly five miles to the south of Ferguson.

The FBI has said the incident was "not directly related" to protests taking place in Ferguson in the wake of the grand jury decision not to indict white police officer Darren Wilson over the killing of black teenager Michael Brown.

FBI spokeswoman Rebecca Wu said one agent was shot in the shoulder and the other was shot in the leg while assisting local police in executing an arrest warrant. Their injuries were not life-threatening.

Wu said: "The incident is not directly related to the Ferguson protests."

The incident took place hours after protesters and police clashed in Ferguson during a second night of demonstrations.

Roughly 2,000 National Guard troops were dispatched to the St Louis area in a bid to help police prevent a second night of rioting and arson following the grand jury verdict.

A total of 44 people were arrested on Tuesday night in Ferguson. A total of 61 arrests were made late Monday and into early Tuesday during a night of arson, looting vandalism and sporadic gunfire, countered by police tear gas and smoke bombs.

Additional reporting by AP and Reuters