Police cordoned off Taupo Quay between the City Bridge and Drews Ave on Saturday morning.
A man is in a serious condition in Wellington Hospital after an alleged assault in central Whanganui.
Police were called to the corner of Victoria Ave and Taupo Quay at about 2am on Saturday after reports the man had been assaulted.
A 23-year-old man is in police custody. Police said
charges were being considered.
A cordon was in place on Taupo Quay between Victoria Ave and Drews Ave in Whanganui's CBD until about 9.30am.
Police are appealing to the public for information from anyone who may have witnessed the assault.
