(CNN) Two United States service members were killed in Afghanistan on Friday, according to a statement from the NATO-led international military coalition in Kabul.

They were killed while conducting an operation, the statement said. There were no further details, and the names of those killed were being withheld until next of kin are notified.

A spokesperson for the coalition told CNN that "the incident is under investigation and we have no additional information to provide."

Two US defense officials told CNN that the US service members were killed during a partnered US-Afghan military operation in Kunduz Province in northern Afghanistan.

The officials added that initial indications are that they were killed during a fight with the Taliban. Afghan troops were also killed in the incident.

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