The target of the strike last Thursday remained unclear but Israeli media reported that a shipment of Iranian arms crossing Syria for use by the Iranian-backed Hezbollah militia in Lebanon was attacked.

	Israeli army Merkeva tanks on the Golan Heights

Syria first reported the incident on the day, saying its air defences had engaged five Israeli planes, but did not say what their target was. Israel remained uncharacteristically silent, pointedly refusing to deny that its warplanes were involved in an operation. The closest it came to acknowledging the affair happened was when it made an undertaking to Turkey to investigate how an Israeli long-range fuel tank was dropped on Turkish territory near the Syrian border.

Another theory gaining ground yesterday was that Israel was deliberately attacking the Russian-made Pantsyr air defence system recently bought by Damascus. The sale includes provision for the Pantsyr system to be shipped on to Iran and it is possible the Israeli attack was co-ordinated with America to probe the effectiveness of the system. It is believed that Iran would use the Pantsyr system to defend its nuclear facilities.

Syria has sought to keep the incident in the public arena, saying yesterday that it had complained formally to the United Nations, accusing Israel of unjustified aggression.

Syria and Israel have fought major wars on three occasions, in 1948, 1967 and 1973, as well as numerous other skirmishes. The two nations remain formally at war although an uneasy calm has largely held for the past three decades. Meanwhile, Israel was contemplating a retaliatory strike on Gaza last night after a Palestinian qassam rocket injured 69 of its soldiers, five seriously, at the Zikim army base. Many of the Israelis were hit by shrapnel as they slept under canvas.

While the rocket was fired by members of the Islamic Jihad party, Israel said it would hold Hamas accountable because the group is the main authority in the Gaza strip since it drove out its Fatah rivals in June.

The Israeli prime minister, Ehud Olmert, convened an emergency meeting yesterday with military and security commanders to discuss a response to the attack.