An Israeli soldier has sparked outrage by posting a photograph appearing to show the back of a Palestinian boy's head in the crosshairs of his sniper rifle on a social networking site.

The context of the picture, posted on the personal Instagram site of Mor Ostrovski, 20, could not be verified but the aggressive message is clear. The minarets and Arabic architecture of the village captured in the background suggest the boy and the town are Palestinian. Ostrovski is an Israeli soldier in a sniper unit.

The Israeli military said the soldier's commanders were investigating the incident. His actions "are not in accordance with the spirit of the IDF [Israel Defence Forces] or its values", a spokesperson said.

Ostrovski, who has closed his Instagram account, told the army he did not take the picture but found it on the internet.

Breaking the Silence, an organisation of veteran Israeli combat soldiers campaigning to raise awareness about life in the West Bank, condemned the image. "This is what occupation looks like. This is what military control over a civilian population looks like," one member wrote on the group's Facebook page.

The image has been heavily criticised online. Electronic Intifada, a news site focused on Palestinian issues, described the photograph as "tasteless and dehumanising". The site published several other images from Ostrovski's Instagram page, including snaps of the soldier posing with heavy-duty guns.

The Israeli military has been hit by a series of scandals from uncensored social media sites, and Electronic Intifada has been one of the more rigorous monitors of offensive postings by Israeli soldiers.

In December, the site discovered Nisim Asis, a 22-year-old soldier from the Beit-El settlement, who posted racist images on his Instagram page, including a picture of himself licking what is probably tomato ketchup from a knife with the caption: "Fuck all Arabs their blood is tasty".

In another unrelated incident, an infantry corps soldier was recently sentenced to 14 days in military prison for posting a picture of himself beside a handcuffed and blindfolded Palestinian on Facebook.

In both these incidents, and the similar case of a female IDF soldier who uploaded lewd images of herself with Palestinian detainees several years ago, military discipline was deemed adequate and criminal investigations dropped.