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JERUSALEM, Aug 10 (Reuters) - A man grabbed a gun from an Israeli security guard and shot him in Jerusalem's Old City on Friday, sparking a gun battle in which the attacker was killed and at least 10 others injured, police and medics said.

Israeli police identified the assailant as an "Arab man" between 18 and 20 years old. An Israeli police commander described the man as a "terrorist", though he did not say what may have motivated the shooting.

The police commander told Israel Radio the man shot the security guard after stealing his gun near a crowded market close to the Church of the Holy Sepulchre in the Old City's Christian Quarter.

A second security guard chased after the attacker and shot him, the commander said. The police and the Israeli emergency service Zaka said the assailant was killed.

"As a result of the gunfire, a number of civilians were injured," the police commander said.

Israeli emergency services said as many as 10 people were injured in the gunfire. Most of the injuries were minor.

The Old City is particularly crowded with shoppers and tourist on Fridays.

One witness told Israel Radio that two security guards shot and killed the assailant.

"I saw the wounded on the ground wasn't moving at all. I didn't see anything in his hands. I saw two security guards continuing to shoot at the man, and the man wasn't moving at all. He was dead," the witness said.

The police commander said in response that only one guard shot the attacker and that he acted "professionally".

In May, Israeli forces killed two Palestinian gunmen during a shootout in Arab East Jerusalem. Two Israeli officers were wounded in the gunfight. There was no claim of responsibility from militant groups for the May shootout.

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