A 42-year-old man charged with raping a woman he did not know on the riverbank in Katherine on Tuesday afternoon has been denied bail, NT Police said.

Police said they arrested the Katherine man on Wednesday for the alleged rape that occurred on Tuesday afternoon. They did not notify the public of the sex assault until Friday afternoon.

“The man’s arrest came after a Katherine woman walked to the riverbank on Tuesday afternoon where she was allegedly sexually assaulted by the man,” police media manager Rob Cross said in a statement.

“The man was unknown to the woman.”

Mr Cross provided no details about how the man was apprehended and why the public wasn’t notified an alleged rapist had been on the loose in Katherine for 24 hours.

The 42-year-old man was remanded and will face Katherine Local Court on October 24, police said.

“Police would like to remind the public to be vigilant when interacting with people unknown to them,” the statement said.

“Members of the public should report suspicious or concerning persons to police to assist in the prevention of these types of crimes.”