They fled, but a police dog tracked them to a river, where two people were arrested. Two others were arrested a short time later. They are believed to be two men and two teenagers, one girl and one boy.
A fifth person, believed to be a male teenager, is still wanted by police.
Both tourists were taken to Whakatane Hospital and their families in Germany were notified.
Police this afternoon said New Zealanders had rallied around the couple.
The Whakatane police station had received an "overwhelming'' number of calls offering donations and accommodation for the couple.
Police asked people to email messages of support to ebop.cib@police.govt.nz to free up the station telephone line.
Officers have recovered items believed to have been used as weapons in the assault but won't say what they were.
Some of the couple's belongings stolen in the robbery are still missing, and police have asked members of the public to look out for objects around the skatepark and river area.
"This is an appalling and mindless attack on a young couple and incredibly sad that this will be their lasting memory of Christmas in our beautiful country,'' Area Commander Inspector Sandra Venables said.
"I must acknowledge both the members of the public who came to their aid and also the officers whose swift actions resulted in a number of early arrests.''
Anyone with information is asked to contact Whakatane police on 07 308 5255, or Crimestoppers, anonymously, on 0800 555111.
- Additional reporting, Matthew Backhouse
