UPDATE 13:00 BST: A military plane carrying soldiers and their families crashed soon after takeoff in a farm field in northern Algeria on Wednesday, killing 257 people in what appeared to be the worst plane crash in the North African nation's history.

The cause of the crash was unclear, and an investigation has been opened, according to a Defense Ministry statement.

Local media reported that the plane crashed just after taking off. Emergency services converged on the area near the Boufarik military base after the crash. Footage from the scene showed thick black smoke coming off the field, as well as ambulances and Red Crescent vehicles arriving at the site.

"There are more than 100 deaths. We can't say exact how many at this point," Mohammed Achour, chief spokesman for the civil protection agency, told The Associated Press.

He said the plane was carrying soldiers. The Defense Ministry did not provide a death toll but expressed condolences to the victims' families.

Ilyushin Il-76
An Ilyushin Il-76 military transport aircraft performs during the International Army Games 2016, in Dubrovichi outside Ryazan, Russia, Aug. 5, 2016. Reuters/Maxim Shemetov

The flight had just taken off from Boufarik, about 30 kilometers (20 miles) southwest of the capital Algiers, for a military base in Bechar in southwest Algeria, Achour said. It was scheduled to make a layover in Tindouf in southern Algeria, home to many refugees from the neighboring Western Sahara, a disputed territory annexed by Morocco.

The Soviet-designed Il-76 military transport plane crashed in an agricultural zone with no residents, Achour said.

The Il-76 model has been in production since 1970s and has an overall good safety record. It is widely used for both commercial freight and military transport.

The Algerian military operates several of the planes.