Algiers: An Algerian military plane carrying soldiers and their families crashed soon after takeoff Wednesday into a field in northern Algeria, killing 257 people in what appeared to be the North African nation's worst-ever plane crash.

Algeria's Defense Ministry said those killed included 247 passengers and 10 crew. The cause of the crash was unclear and an investigation has been opened.

Algerian authorities did not mention whether there were any survivors but one witness reported seeing some people jump out of the aircraft before it crashed at 7:50 am Wednesday local time.

The flight had just taken off from the Boufarik military base, 30 kilometres southwest of the capital Algiers, for a military base in Bechar in southwest Algeria, according to Farouk Achour, the chief spokesman for the civil protection services.

It was scheduled to make a layover in Tindouf in southern Algeria, home to many refugees from the neighbouring Western Sahara, a disputed territory annexed by Morocco.