Israel's prime minister is defending the military after footage emerged of a soldier lethally shooting a Palestinian attacker who had already been shot and subdued.

Benjamin Netanyahu has previously said the incident in question does not reflect the military's conduct, and on Sunday said criticism of the armed forces as a whole over the incident is "outrageous and unacceptable."

The military has arrested the soldier and opened an investigation into what it said appeared to be a "grave breach" of its values.

Several right-wing lawmakers have come to the soldier's defense, accusing detractors of abandoning him before he was given a fair hearing. Hundreds protested outside the prison in which he is being held, and posters have surfaced denouncing the defense minister and military chief.