"It was in the northeastern part of Bamiyan province. If that is the case, and that seems to be the information we have, then I think that's good news if it makes Afghanistan a safer place for our people."
Mr Key said the attack on Kalta happened last week and he did not know if the families of the dead soldiers had been told yet.
He said the main aim was to make the environment safe and it was understood further attacks on the Taliban were planned.
"We're in a war zone and ultimately we need to make sure that our men and women are best protected as we can and that means using intelligence and if required making sure that those who are undertaking those attacks aren't in a position to do so."
Radio New Zealand's Afghanistan correspondent Jon Stephenson said coalition officials released a statement yesterday which said Kalta was responsible for several attacks on Afghan and coalition forces in Bamiyan Province and was also a mentor for insurgents.
The operation to kill Kalta was carried out by international forces, Stephenson said.
Mr Stephenson said he had been told the Provincial Reconstruction Team had provided intelligence behind the airstrike but that was yet to be confirmed.
He said it was likely that coalition or Afghan special forces on the ground called in the airstrike "but whether or not new Zealand played a role in that is far from clear. Certainly there would have been a very strong intelligence component behind this raid."
He said Kalta's death would be a major blow for the Taliban.
"He was clearly, by all accounts, a very resourceful, a very well informed insurgent leader, who played a very active role in both Baghlan and Bamiyan.
"He had as recently as September reportedly been behind an attack on the district officers in Shibar that had lasted for about one and a half hours and he had escaped apparently over the border back into Baghlan on that occasion."
Kalta would have been a "highly prized target" of coalition and Afghan forces, Stephenson said.
Last month the Defence Force, Mr Key and Defence Minister Jonathan Coleman denied SAS personnel had been sent to Afghanistan on a so-called revenge mission for the New Zealand soldiers' deaths.