The police chief of a Texas Gulf Coast city has apologised after two white male police officers mounted on horseback led a black, handcuffed trespassing suspect by a rope through downtown streets.

Photos of the astonishing Saturday arrest were widely circulated on social media, with many commenting on the appearance of a black man being led by mounted officers through city streets.

Galveston police Chief Vernon Hale said in a statement on Monday that while his officers used a technique that’s acceptable in some situations, such as with crowd control, they “showed poor judgment in this instance and could have waited for a transport unit at the location of arrest”.

Hale said his department has “immediately changed the policy” to prevent further use of the technique.

The officers had linked the rope to handcuffs worn by 43-year-old criminal trespass suspect Donald Neely and led him to a mounted patrol staging area.

Hale told The Galveston County Daily News that he regularly talks to his officers about how their actions affect people’s perception of the department.

“You have to be aware of the images we portray,” he said. “We talk about it when we talk about use of force, when we talk about vehicle pursuits. Quite frankly, I never would have dreamed of it in the context of mounted officers.”

Mary Patrick, president of the Galveston chapter of the NAACP, told the newspaper that the department had an obligation to explain the officers’ actions to the public.

Patrick later said she had spoken with Hale and the police chief had the NAACP’s support.

Hale has been released on bail.