Israeli soldier Elor Azaria is embraced by his mother at the start of is sentencing hearing at a military court in Tel Aviv, Israel February 21, 2017. REUTERS/Jim Hollander/Pool

GENEVA (Reuters) - The United Nations’ human rights office said on Friday that an 18-month sentence handed down to an Israeli soldier for killing a wounded Palestinian was “excessively lenient” and “unacceptable”.

The soldier, who shot Abdel Fattah al-Sharif Elor in the head after he was incapacitated following a knife attack in March 2016, was sentenced to 18 months’ imprisonment on Tuesday. The show of leniency drew Palestinian outrage.

“We are deeply disturbed at the lenient sentence given by the Tel Aviv Military Court earlier this week to an Israeli soldier convicted of unlawfully killing a wounded Palestinian in an apparent extrajudicial execution of an unarmed man who clearly posed no imminent threat,” U.N. human rights spokeswoman Ravina Shamdasani told a news briefing in Geneva.

Manslaughter carries a maximum punishment of 20 years under Israeli law, she said.

“This case risks undermining confidence in the justice system and reinforcing the culture of impunity,” Shamdasani said. “This is a chronic culture of impunity we are talking about.”

More than 200 Palestinians have been killed by Israeli security forces since the most recent upsurge in violence began in the West Bank in September 2015, she said.

Sergeant Elor Azaria is the only member of the Israeli security forces to have been brought to trial for such a killing, she added.

Palestinian President Mahmoud Abbas is due to address the U.N. Human Rights Council in Geneva on Monday at the start of its main annual session that lasts until March 24.

Israel, backed by its main ally the United States, says that the 47-member state forum is biased against it due to its frequent resolutions condemning Israeli settlements in the occupied West Bank and practices in the Gaza Strip.