The Wicker remains closed this morning, between Savile Street and Derek Dooley Way, as officers continue to conduct enquiries.
Police believe the trouble may have started at the Niche nightclub on Walker Street, before spilling onto the street.
Officers were called to the Wicker at around 4.50am to reports of a man with stab wounds.
On arrival, three more men with suspected stab or slash wounds and another with injuries believed to have been sustained in an assault.
All five men, aged 21, 22, 23, 39 and 42, were taken to hospital. None of their injuries are believed to be life-threatening.
Police said officers were still speaking with the victims in an attempt to get descriptions of the attackers.
Anyone who was in the club or the surrounding area, especially those who believe they witnessed the attack, is asked to call police on 101 or Crimestoppers, anonymously, on 0800 555 111, quoting incident number 286 of December 23.