By Jonathan Marcus

Diplomatic correspondent, BBC News



Israel has kept up a careful policy of silence over the accusations

Later unidentified drop tanks, which may have contained fuel for the planes, were found on Turkish soil near the Syrian border, indicating perhaps the Israeli jets' exit route.

The Syrian authorities are livid. They say that the aircraft were driven off but that they fired their weaponry into a deserted area.

The implication is that the planes effectively dumped their munitions so better to manoeuvre during their escape.

The Syrian government has briefed Western diplomats and complained to the United Nations.

But there have been no images of the empty countryside where the weapons are alleged to have landed.

Israeli sources are saying nothing.

Long-standing contacts are uncharacteristically silent, noting only that Israel's military censorship on this subject is as tight as they can ever remember.

Mood of satisfaction

From Washington has come some partial illumination of the shadows.

US officials indicate that at least one target in northern Syria was hit and despite the Israeli silence there does seem to be a perceptible mood of satisfaction in Israel; a sense that what they wanted to achieve was carried out.

So what actually went on during the early hours of Thursday morning? Why were Israeli jets over Syria at all?

And if they indeed released weapons, what were they firing at?

Initially experts suggested that this might simply have been an over-flight to trigger air defence radars and gather electronic intelligence.

Such a probe might be linked to new air defence missiles reportedly supplied to Syria by the Russians.

Other pundits wondered if a potential strike path to Iran was being tested out; though a southern route here into US-controlled Iraqi air-space would be more logical.

And neither option would explain why such aircraft might be armed with air to ground weapons.

North Korea link

As far as likely targets of any attack go there are two broad suggestions.

One, cited by the New York Times newspaper quoting a US source, suggests that the attack was in some way linked to North Korea.

The former US ambassador to the UN, John Bolton, in a recent article in the Wall Street Journal, raised the possibility that Syria is sheltering technology or materials relating to North Korea's nuclear programme.

When I spoke to Mr Bolton in London just the other day he strongly defended this thesis though he would not be drawn on the reliability of his sources.

Another suggestion is that maybe a missile store or factory with weaponry heading to Hezbollah in Lebanon was hit.

Israel has long complained that the Damascus government is at the very least turning a blind eye to such weapons supplies coming from Iran.

Maybe Israel decided to send the Syrian government a message that it would understand.

Muted response

What is intriguing is that the response of both the Syrian and Israeli governments has been muted - in the Israeli case largely mute.

The Syrians, while angry, are clearly embarrassed that something may have occurred that they failed to prevent.

Israel and Syria remain technically at war

Israel's deterrent capacity, weakened by the summer 2006 war in Lebanon, is partially restored.

But an explanation too is needed for Israel's silence.

Maybe it does not want to over-play its hand.

This apparent raid comes after a summer of tensions between the two countries which some feared might lead to open warfare.

During the past few weeks tensions have markedly declined.

Indeed prior to the bombing mission, if that is what it was, Israel reportedly sent messages to Syria via an intermediary, indicating that it was scaling down its forces on the Golan Heights.

Was this an effort to ensure that this "raid" was not interpreted by the Syrians as a prelude to a large-scale Israeli attack?

There are still more questions than answers in this affair. More information is slowly seeping out.

But in many ways it is remarkable that in an age of instant news and the worldwide web spreading information almost at the speed of light, there can still be episodes like this that remain shrouded in so many layers of mystery.