An Airbus plane operated by Lufthansa's Germanwings budget airline crashed in southern France on Tuesday en route from Barcelona to Duesseldorf, police and aviation officials said.
French Prime Minister Manuel Valls said he understood between 142 and 150 people were on board and feared dead.
"The cause is at present unknown," he told reporters.
A spokesman for the DGAC aviation authority said the airplane crashed near the town of Barcelonnette about 100 km (65 miles) north of the French Riviera city of Nice.
The Airbus plane had taken off from Barcelona airport at 0855 GMT, a spokeswoman for Spain's airport operator Aena said.
The spokeswoman declined to give any additional detail on the plane or who was on board.
Lufthansa's Germanwings yet to confirm plane crash
Lufthansa did not have any information following reports of a plane crash in France and said it could not confirm that an incident had occurred, a Lufthansa spokesman said.
Police and aviation officials have said an Airbus plane operated by Lufthansa's budget carrier Germanwings crashed in southern France on Tuesday en route from Barcelona to Duesseldorf.
Germanwings said on its Twitter feed that it would inform media on its website as soon as it had more information.
INFO: We have recently become aware of media reports speculating on an incident though we still do not have any own confirmed information...
— Germanwings (@germanwings)
March 24, 2015... As soon as definite information is available, we shall inform the media immediately ...
— Germanwings (@germanwings)
March 24, 2015The crashed A320 is 24 years old and has been with the parent Lufthansa group since 1991, according to online database airfleets.net
Hollande says believes no survivors in plane crash
French President Francois Hollande said he believed none of the 148 people on board the Germanwings plane that crashed on Tuesday had survived.
"There were 148 people on board," Hollande said. "The conditions of the accident, which have not yet been clarified, lead us to think there are no survivors."
He said there was likely to be a significant number of German victims.
He added: "The accident happened in a zone that is particularly hard to access."
Accident agency sends team to crash site
France's BEA accident investigation agency said on Tuesday that it was sending a team of people to investigate the site of a Germanwings plane crash in southern France.
"We can confirm the accident and we are putting in place a team to head to the site," a BEA spokeswoman said.