Washington - Three police officers were killed and three injured in a shooting in Baton Rouge, Louisiana on Sunday, with at least two suspects at large, police said."Three law enforcement [officers] are confirmed dead, three others injured," the East Baton Rouge sheriff's office said in a statement. "One suspect is dead, law enforcement believes two others may be at large."The shooting took place along a highway around 09:00 (13:00 GMT), the statement added.It appears the shooting began before police officers were at the scene."It's my understanding that they [the officers] had responded to an initial shooting incident," Casey Rayborn Hicks, public affairs officer for the sheriff's office, told local WAFB television.Police are looking for the two suspected surviving shooters."We're not sure of anything right now," Baton Rouge police spokesperson L'Jean McNeely told reporters near the scene, urging local residents to be on the alert for the suspects."If they're wearing all black, army fatigues, anything that's suspicious in nature," citizens should notify police, he said of the suspects' possible appearance.Injured police in critical conditionThe injured police were reported to be in critical condition.WAFB aired video footage of police responding to the scene. Multiple shots could be heard as civilian cars quickly backed away.There were conflicting reports about the shooting, with WBRZ television reporting a witness describing a man dressed in black with his face covered who started shooting indiscriminately.Video posted online showed a SWAT team en route to the scene."This is an unspeakable and unjustified attack on all of us at a time when we need unity and healing," Governor John Bel Edwards said in a statement. "Rest assured, every resource available to the state of Louisiana will be used to ensure the perpetrators are swiftly brought to justice."The shooting is the latest in a series of high-profile killings that have shocked the country over the last several weeks, exposing deep fault lines in society and reviving long-running debates about racial prejudice and an epidemic of gun violence.A gunman killed five police officers in Dallas earlier this month during a demonstration triggered by the fatal police shooting of two African-American men whose dying moments were captured in shocking video footage that went viral online.One of those killed was Alton Sterling, shot dead by a police officer in Baton Rouge two days before the Dallas attack.Last week, police arrested more than 100 protesters taking part in a demonstration against police brutality in Baton Rouge under the banner of the Black Lives Matter movement.Last month, Democratic lawmakers, pushing for tougher gun-control laws after a massacre in a Florida gay nightclub killed 49 people, staged a virtually unprecedented 24-hour sit-in in Congress after Republicans refused to allow a vote on two widely supported measures.