WATCH: Baltimore police officer appears to spit on man after handcuffing him
Baltimore police officer appears to spit on a handcuffed suspect (YouTube)

A Baltimore police sergeant has been suspended and a criminal investigation launched after video posted online apparently showed the officer spitting on a handcuffed suspect, the police department said on Tuesday.

Cell phone video captured from the incident on Monday appeared to show Sergeant Robert Mesner, a 34-year veteran of the force, spitting on a detained man in a "prone position," interim Police Commissioner Kevin Davis told a media conference.

A bystander's voice in the video is heard yelling "he just spit on him."

Davis said internal and criminal investigations have been launched.

"We have serious concerns about it," Davis said.

Mesner could not be reached immediately for comment.

The suspect in the video had been arrested on charges including second-degree assault of a law enforcement officer and disorderly conduct, authorities said.

The Baltimore Police Department is due to roll out body-worn cameras for officers soon to help lend transparency to police interactions with the community.

"More and more police encounters are going to be captured on videotape," Davis said. "The police department welcomes that."

Last week, video captured by a bystander on a major city street and posted online showed a man punching a police trainee and knocking him to the ground.

Davis became interim head of the Baltimore police in July. He replaced former Commissioner Anthony Batts, who had come under heavy criticism after an unarmed black man died of injuries sustained while in police custody in April.

The death of Freddie Gray, which came after months of protests over police use of force in the United States and allegations of racial bias by law enforcement officials, sparked the worst rioting seen in Baltimore in half a century.

Watch video of the encounter posted online by Carlos El Hombre:

(Reporting by Victoria Cavaliere)