Israel's army says it is investigating the death of a Palestinian activist who died after being hit in the face by a tear-gas canister at the weekend. Pictures of the incident appear to show Mustafa Tamimi, 28, being shot at from close range. He was among a small group of Palestinians throwing stones at Israeli military vehicles when he was struck. At his funeral on Sunday, there were further clashes between mourners and Israeli soldiers. Photographs of the incident in the Palestinian village of Nabi Saleh show Mr Tamimi apparently being shot at from the back of an Israeli military vehicle. This would be seem to be a contradiction of the army's own rules governing the firing of tear gas, says the BBC's Wyre Davies in Jerusalem. Although Mr Tamimi was immediately transferred to hospital, he died from his injuries the next day. The Israeli army called the death an "exceptional incident" and has promised a full inquiry. But human rights groups say Mustafa Tamimi was at least the 20th person to have been killed in recent years at demonstrations in the West Bank. The protest in Nabi Saleh is held weekly against the construction of Jewish settlements and the separation barrier on occupied Palestinian land.