A man is in custody after allegedly assaulting as many as nine women in central Auckland on Saturday in a series of "serious incidents".

"Police responded to reports that a number of women had been assaulted by what was believed to be the same man at various locations in central Auckland between around 1:30pm and 2:50pm this afternoon," a police spokesperson says.

"A 35-year-old man was apprehended by police on Elliot Street around 2:50pm."

Police have received nine complaints so far, and are speaking to a number of victims.

"An investigation into these incidents is underway," a police spokesperson says.

"Police urge anyone with any information, including anyone who saw anything concerning in central Auckland between around 1:30 and 2:50pm this afternoon, to contact police straight away on 09 302 6557 or Crimestoppers anonymously on 0800 555 111."