Syria said its anti-aircraft defences opened fire on an Israeli warplane yesterday after the craft violated its airspace, at a time when border tensions between the two old foes have been soaring.

The official Syrian news agency said that “enemy Israeli planes penetrated Syrian airspace from the Mediterranean Sea heading towards the northeast, breaking the sound barrier. Our air defences repulsed them and forced them to leave . . . after, the Israeli planes dropped munitions, without causing human or material loss.”

It was unclear, however, what the Israeli plane had dropped, sparking speculation in the Israeli press that the aircraft might have jettisoned a fuel tank during manoeuvres.

Israel’s high command refused to comment on the Syrian allegations, which come after months of mounting suspicion between the two states. Israel has been carrying out major military exercises in the occupied Golan Heights, snatched from Syria in the 1967 war, to re-train its army after its unsatisfactory performance against Lebanon’s Hezbollah in last year’s month-long war.

Syria meanwhile is reported to have massively increased its arsenal of Russian-made anti-aircraft missiles in the border area.

"Syria retains the right to determine the quality, type, and nature of our response to the Israeli attack," said Mohsin Bilal, the Syrian Information Minister. "The Syrian leadership is seriously considering its response," he said, without indicating whether the response would be diplomatic or military.

The Israeli Government has been sending out reassuring messages to Syria that it does not seek a fresh war, even as it prepares for what many in the military see as an inevitable renewal of fighting with the undefeated Hezbollah, supplied with weapons by Syria and its ally, Iran. Fears have been increasing recently that an incident such as yesterday’s reported overflight could accidentally trigger a sudden conflict with Damascus.

Syrian officials said an investigation was under way to determine what, if anything, the Israeli warplane had dropped.

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