Nidal Hasan was sentenced to death by a military jury in 2013 for carrying out the Al-Qaeda inspired mass shooting at Fort Hood, Texas. (AFP pic)

WASHINGTON: President Donald Trump has approved the execution by firing squad of Nidal Hasan, a US Army psychiatrist who shot dead 13 people at a military base in 2009, the Pentagon said on Monday.

Hasan's execution for the attack at Fort Hood in Texas - which also wounded more than two dozen people - will be the first carried out by the US military since 1961.

Defense Secretary Pete Hegseth "has recommended - and President Donald J. Trump has approved -- death by US Army firing squad for convicted terrorist Nidal Malik Hasan," Pentagon spokesman Sean Parnell said in a post on X.