A manhunt has been launched to find two young men who were filmed slapping and taunting an elderly man on a subway train in Chicago.

The men, both African American in their late teens or early 20s, towered over their victim as they laughed and jumped around him, hitting his head, on a CTA Blue Line train.

At one point the slaps become so hard they are audible on the clip, which was filmed by their friend and posted on Facebook.

SCROLL DOWN FOR VIDEO

Launching their attack: The conflict on Chicago's CTA Blue Line train started with this slap, filmed by a friend

Escalated: Another friend leaped into the action and laughed loudly as he jumped around slapping the old man

Though the man tries to kick back and gingerly lifts an arm to swipe at them, they cackle with laughter and jump out the way.

Police are now appealing for anyone that recognizes the men in the video to come forward.

Defending the attack, one of the group - which remains at large - called radio station WBBM to say the white victim had but touting racial slurs.

'We didn't do nothing. We got on the train and he was saying some racial slurs,' he says.

Flinching: The attacker menacingly holds his hand over the man who is quivering with fear before he is hit

Tries to defend himself: The man gingerly stands up to defend himself but the attacker pushes him back

The young man calls himself 'A-T-L.' He says he didn't take part in slapping the man.

'I don't know why they did what they did,' he tells WBBM. 'I just recorded it because it was funny.'

A spokesman for the CTA said: 'Though this crime apparently was not reported, because neither CTA nor Chicago Police have a report of the incident, we are pulling additional video to share with police as part of a now-open investigation.

'We encourage members of the public who witness a crime to report it immediately, especially if they have evidence such as a video. Incidents like this are rare on the CTA.'