The eruption of the White Island volcano, leaving at least five people dead and many unaccounted for, has dominated international headlines.
Nine News has reported that 24 Australians are understood to have been on White Island when the volcano erupted this afternoon.
US Ambassador Scott Brown said his heart goes out to the victims and their families involved in the disaster.
"Gail and I are so very sorry to hear the devastating news from Whakaari / White Island. Our hearts go out to the victims & their families," he wrote on Facebook.
"Thank you to the brave emergency personnel doing everything to help."
One witness to the eruption told the BBC he was at the crater only 30 minutes before the eruption.
"It was still safe-ish but they were trying to limit the group sizes [of people visiting the volcano]."
Describing the eruption, he said: "We had just got on the boat ... then someone pointed it out and we saw it. I was basically just shocked.
"The boat turned back and we grabbed some people that were waiting on the pier," he told the BBC.
The Washington Post and The Guardian are also reporting on the event.