"I've given them messages of solidarity once I managed to find out they were okay, but now it's just that horrible point of waiting to hear the list of names to see if there are any I know less well who were involved," Ms Ardern said.
She was also trying to find out if there will be a memorial service.
"If there is, I will try to make an effort to go. I'm just not sure what's happening at this point in time."
Ms Ardern was on the board of the International Union of Socialist Youth (IUSY) for six years, which Norway's AUF was actively involved with. She travelled with some members of Norway's young Labour group to places including Lebanon, where they worked on various projects together.
A New Zealand teenage girl, who has dual New Zealand and Norwegian citizenship, was believed to be on the island at the time of the shooting and remains missing.
The New Zealand Ministry of Foreign Affairs and Trade said today the New Zealand embassy was in direct contact with the teen's family but she had so far not been traced.
Witnesses said the gunman moved across the small, wooded Utoeya holiday island on Friday firing at random as young people scattered in fear.
He has since admitted sole responsibility for the rampage and was due to appear in court today.
- NZPA
