Two Italian military jets have collided in mid-air during a training exercise in eastern Italy.
The aircraft crashed 30km (18 miles) from Ascoli in the Marche region on Tuesday, setting off raging fires in the forest below.
Four people are thought to be missing, including both the pilots and navigators.
Local reports had indicated that the two pilots had ejected, but they have not been confirmed.
No casualties have been reported on the ground.
"A giant ball of fire lasted for five seconds before slamming into the mountains", Fabio Valeri, who witnessed the crash, told Italian news channel Sky TG24.
Residents in the nearby villages of Olibra and Venarotta described hearing a bang before the fire broke out on the ground.
A search and rescue operation was being carried out by local firefighters and police and Italian media said parts of the planes had been found.
"Our first concern is to find the crews," an air force spokesman told Ansa news agency.
The two planes were based at Ghedi in north-west Italy. They had been flying low at the time of the collision, reports say.