A man who allegedly took part in a vicious attack in Darwin has been rounded up by police after he took off his top and ran around, showing his name tattooed across his back.

The man was with another man outside a convenience store in busy Mitchell Street about 10:30pm on Sunday when the pair asked a 27-year-old man whether he wanted to buy marijuana, police said.

When the man they had approached refused the offer, the two men, aged 21 and 22 and from interstate, allegedly punched and kicked the victim.

"After the assault they took their shirts off, placed them around their heads and ran around the block," Duty Superintendent Louise Jorgensen from NT Police said.

"Helpfully one of the offenders had his name tattooed on his back, so it wasn't hard to locate him.

"We found him at a nearby bar and he was arrested."

The victim suffered serious facial injuries and was taken to hospital for treatment.

After the two men were arrested one of them went into a police van but the other one allegedly fought officers.

"The offender that was in the van got out and helped the police put his mate inside," Superintendent Jorgensen said.