A plane has crashed in southern Afghanistan, killing four international service members.
Initial reporting indicated there was no enemy activity in the area at the time, but coalition personnel secured the site and the cause of the crash was being investigated, Nato said.
The brief statement did not identify the nationalities of the victims, or say where the plane went down.
However, Mohammad Jan Rasoulyar, deputy governor of the southern province of Zabul, said an aircraft belonging to foreign forces crashed on Saturday afternoon in Shah Joy district.
He said the site had been surrounded by international forces.
In an announcement earlier, the Taliban vowed to step up violent attacks now that winter was over and warmer weather has made travel and fighting easier.
The militant group said it would use every possible tactic to "detain or inflict heavy casualties on the foreign transgressors."
Taliban fighters, who seek to replace the elected Afghan government with one promoting a stricter interpretation of Islamic law, named their offensive after a legendary Muslim military commander, Khalid ibn al-Walid.
The Taliban threatened to infiltrate the Afghan security forces and conduct more attacks on Afghan policemen and soldiers as well as foreign troops.
Such attacks threaten the strength of the Afghan forces as they work to take over responsibility from coalition forces. The latest one occurred in March, when a member of a government-backed village defence unit shot and killed five of his colleagues in Badghis province in northwest Afghanistan.