Image copyright Reuters

Police in Chicago say they are investigating a suspected homophobic and racist attack on a star of the US TV drama Empire.

Jussie Smollett needed hospital treatment after two men punched him in the face and poured an unknown chemical substance on him, police said.

One of the attackers wrapped a rope around his neck before both fled the scene in the early hours of Tuesday.

Police said they were treating the incident as a possible hate crime.

Smollett has since been discharged from hospital, the TMZ website reported. Police described his condition as "good".

The incident happened at East Lower Water Street, Chicago, at about 02:00 local time as the actor was leaving a restaurant.

"Two unknown offenders approached him and gained his attention by yelling out racial and homophobic slurs," a police statement said.

The chemical substance poured on Smollett was not named, but some media reports said it was bleach.

"At some point during the incident, one of the offenders wrapped a rope around the victim's neck," the statement added.

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Investigators are appealing for witnesses and any video of the incident.

Smollett, who plays a gay character in Empire, had earlier posted on Instagram that he was tired having arrived in Chicago after "seven hours on a plane for a two hour flight".

Empire centres on a hip-hop music and entertainment company and the drama among the family members that run it.