A Jewish Israeli man was shot and killed at Jerusalem's Western Wall today as hundreds of worshippers began early morning prayers at the site - the most holy in Judaism.

The middle-aged man, who has not yet been identified by police, is understood to have shouted the Arabic phrase, Allahu al-Akbar, or God is the Greatest, before a private security guard opened fire, killing him instantly.

The phrase, though commonly used in Arabic speaking countries, is often associated in the West with terrorist activity. It is usually shouted by suicide bombers just before they detonate their explosive. There has been little major terrorist activity in Jerusalem in recent years, although suicide bombings were commonplace just a few years ago.

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The man's motives are not known, but local media reports suggested that he was a regular visitor to the site. "I don't understand why he was shot. Everyone here knows him and his behaviour. He has often acted nervously. What happened here isn't normal," David Dahan, who was at the Western Wall at time of the shooting, told the Israeli news site, YNet.

A resident of Jerusalem's Old City, told YNet: "The security guard should have first shot in the air, even if the guy was crazy he should have shot his foot, not straight at the chest. He made a mistake by shooting him with so many bullets. I don't understand why he shot him with 10 bullets. He doesn't do anything. Why didn't the security guard stop after one bullet? I'm so sorry for him."

Police spokesman, Micky Rosenfeld, said that the guard, who is believed to be in his mid-twenties, "fired a number of shots" after the man shouted the phrase. Reports indicate that the dead man's hands were in his pockets at the time, and that the guard believed him to be acting suspiciously.

"The fact he shouted Allahu al-Akbar, that seems to be why the security guard drew his weapon and fired a number of shots at him," Mr Rosenfeld said. "We are looking into what (the dead man's)... motives were."

The guard is understood to have told police that he believed the man was an Arab and was about to launch an attack. When asked by the Associated Press if a weapon was found on the man's body, Mr Rosenfeld said he had no more details.

The guard was arrested and questioned by police. He is later appeared in court on suspicion of murder and his detention was ordered until Tuesday. His identity was not given, and he did not speak during the hearing.

The Western Wall and its surrounding complex is one the biggest flashpoint spots in the Arab-Israeli conflict. On top of the Western Wall sits the Temple Mount, which Sunni Muslims regard as their third most sacred location, behind Mecca and Medina in Saudi Arabia. It is often the scene of violent clashes between Israelis and Palestinians.