The Israeli military has charged a soldier who shot a wounded Palestinian assailant as he lay on the ground with manslaughter.

The defendant, a conscript infantry medic whose name has been barred from publication, was captured on video firing once into the head of the man after he had been shot by other soldiers while taking part in a stabbing attack on 24 March.

The incident in Hebron, a city in the occupied West Bank that has been a focus of a six-month-old wave of Palestinian street violence, tapped into international controversy over whether the response of the Israeli security forces has been heavy-handed.

Defence lawyers say the soldier took action fearing the Palestinian had a hidden bomb. Prosecutors, citing testimony by the soldier’s comrades and his apparently calm disposition, see it as an illegal shooting motivated by revenge.

The soldier was initially held on a murder warrant. The lesser manslaughter charge, reflecting a view that the killing was not premeditated, could mean a jail term of up to 20 years.

“The terrorist ... was left lying on the ground, still alive, and did not present any immediate and tangible danger to the civilians and soldiers around him,” the manslaughter indictment said.

It said the accused handed his helmet to a comrade, cocked his rifle, walked a few steps towards the Palestinian and “fired one bullet at the terrorist’s head”, causing his death.

Such action, the charge sheet said, violated rules of engagement and had no “operational justification”.

An opinion poll last month found that 57% of Israelis thought the soldier should never have been arrested. His supporters, including some rightwing politicians, have demonstrated for his release. Almost 60,000 people have signed an online petition demanding he be decorated for heroism.

The soldier’s family and supporters planned to hold a rally under the slogan of “you don’t abandon a warrior” in a Tel Aviv square on Tuesday.

Two popular Israeli singers initially said they would perform at the gathering, but later withdrew, saying they feared the event would have political overtones and be seen as a protest against military authorities.

The outcry over the Hebron incident has flagged up rare rifts over the role and ethics of Israel’s conscript armed forces.