A Texan police chief has apologised after two white male officers on horseback led a black, handcuffed trespassing suspect by a rope through city streets.

Key points: The suspect was accused of trespassing and was known to police

The suspect was accused of trespassing and was known to police The arrest was acceptable under Texan police policy

The arrest was acceptable under Texan police policy The police chief said the policy had since been changed to prevent further use of the technique

Photos of the arrest on Saturday in Galveston, about 80 kilometres south-east of the state's largest city, Houston, were widely circulated on social media and drew comparisons to images of the slave era.

In a statement, Galveston police chief Vernon Hale said that while his officers used a technique that was 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".

"My officers did not have any malicious intent at the time of the arrest," he said.

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.

In a press release, police said Mr Neely had been warned against trespassing in the same area on several occasions.

Some American observers likened the photo to images of the slave era, or that of the Jim Crow era — a term that describes a period where racial segregation was legally enforced between African Americans and white Americans in the southern United States from the end of the Civil War until 1968.

Many African Americans and other non-white Americans during this period lived under the fear of lynchings, which was most commonly associated with images of public hangings triggered by mob violence.

American education initiative, Monroe Work Today, estimated that almost 5,000 people of colour were murdered by lynchings during this period.

Derek Litvak, a doctoral student specialising in America's 18th and 19th-century race, slavery and constitutional history at the University of Maryland, wrote on Twitter: "1819 or 2019, the slave coffle hasn't left us."

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Texan Democratic presidential candidate Beto O'Rourke said police actions demanded accountability and justice.

"We need to call this out for what it is: racism at work," he wrote on Twitter.

The BBC reported that the person who took the image wanted to remain anonymous.

Police 'have to be aware of the images we portray'

Mr Hale said his department had "immediately changed the policy" to prevent further use of the technique.

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He told The Galveston County Daily News he regularly talked to his officers about how their actions affected 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."

Mr Neely is free on bond but has no listed telephone number and could not be reached for comment.

Mary Patrick, president of the Galveston chapter of the National Association for the Advancement of Coloured People (NAACP), told the newspaper the department had an obligation to explain the officers' actions to the public.

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

ABC/AP