Syrian government blames Aleppo university bombing on extremist group al Nusra

The UN Secretary General has called the attack on the University of Aleppo that killed more than eighty people a war crime.

Or rather, he almost did.

In a half hearted statement, Ban Ki Moon said the attack was "heinous" but instead of labelling it a war crime, he simply warned that targeting civilians amounts to such a crime.

You might accuse me of hair-splitting, but it's an important distinction. It either is or is not a war crime to kill 87 people, most of them students, regardless of exactly who did this.

And that's where his hesitation is born.

It's still not certain who launched this attack.

There are claims and counter claims from eye witnesses and deadly enemies.

Some students say they heard a MiG fighter plane just before the explosions. This is possible. They operate in the skies above Aleppo and they have attacked in the past.

Activists who oppose President Assad say regime forces attacked the university.

The obvious question is why would a government warplane attack a government university in a government held area of the country's biggest city?

There is no logical answer. There was no threat at the university at the time to the army.

Enemies of the government will of course say the regime doesn't need a reason; it's just evil and is sowing more seeds of mayhem.

The government's explanation is different. It said initially two rockets were fired from a rebel-held area of the city and hit the university.

Of course it is possible that rockets were fired at a MiG, missed and hit the buildings. Except the trajectory of rockets fired a kilometre into the sky is unlikely to take them into the side of buildings in two explosions several minutes apart.

The government has now changed its position. Syria's Information Minister has just given me another explanation.

Omran al-Zouabi says the Islamist extremist group Jabhat al Nusra is responsible.

He says the twin explosions a few minutes apart, the intent to kill large numbers of people, the targeting of a government building and the capability of the group to do such a thing, all points to them as the most likely perpetrators.

Al Nusra does indeed go in for spectacular mass killings. It was responsible for the attack on the army headquarters using a suicide bomber, a bomb inside and many gunmen.

It, rather than the Free Syria Army, has shown its has the capability of exploding massive bombs outside buildings.

But al Nusra doesn't claim its attacks. Its policy is secrecy; deeds not words.

So the truth may prove elusive for a while longer.

But whatever the truth of who exactly did this, what happened is clear.

And it's clear Ban Ki-moon is still reluctant to tread on toes in Syria by labelling a massacre "a war crime".