Scene of the attack
Scene of the attack Reuters

Three police officers have been killed and three others wounded after gunmen opened fire on police headquarters in Baton Rouge, Louisiana, according to reports.

The incident occurred at 9:30 Sunday morning, according to senior police official William Daniel.

East Baton Rouge Mayor-President Kip Holden has called for the public to pray for the victims and their families.

"There is still an active scene. They are investigating," he told CNN. "Right now we are trying to get our arms around everything."

An informed source told CNN police were called to respond to a "suspicious person walking down Airline Highway with an assault rifle." Officers who arrived at the scene to investigate were gunned down.

According to initial reports one gunman was shot dead by police, while up to two accomplices are believed to still be at large.

Louisiana Gov. John Bel Edwards denounced the "unspeakable and unjustified attack on all of us at a time when we need unity and healing."

The deadly attack comes 10 days after a US Army veteran affiliated with Black extremist organizations murdered five police officers and wounded several others in a shooting during a "Black Lives Matter" protest against police brutality in Dallas, Texas, called after a spate of killings by black suspects at the hands of police.

Gunman Micah Xavier Johnson was eventually killed by police.