Posted April 04, 2017 12:22:00

Photo: A victim of the St Petersburg metro explosion is carried away by rescuers (Reuters: Anton Vaganov)

Even before the acrid smoke had cleared, the dead and injured removed from the train station, Russia's security organisations were hard at work trying to answer the basic questions: who did it, why, and what are the risks of further attacks?

It is the first time the St Petersburg metro, which moves 2 million people a day, has been attacked like this.

But in 2009 a high speed train running between Moscow and St Petersburg was hit, killing 27 and injuring 130 others.

One year later, the Moscow Metro was attacked by two suicide bombers leaving 38 dead.

Rail systems are always vulnerable with so many travellers using multiple entry and exit points. You just can't monitor everyone.

Russia has a long history of terrorism.

In the late 1990s the separatist struggle in Chechnya saw outrages committed by both sides, Government and rebel.

Blocks of flats were bombed in Moscow, and the horrendous massacre of children in the Beslan school siege in 2004 represented a new low of depravity.

In previous years the almost automatic assumption would have been any attack was related to that ghastly conflict.

But there are new possibilities.

When Russia played its hand in Syria, launching a bombing campaign to tip the balance of power in President Bashir al-Assad's favour, Moscow created a whole raft of new enemies.

A former Chechen general warns Moscow's intervention in Syria could degenerate into a similar bloody mess.

Not only has so-called Islamic State felt the devastating force of Russian bombs, but so too the myriad of opposition groups driven out of places like Aleppo.

All have a deep hatred of Russia. Most have military training and many of their foreign fighters, up to 7,000 of them, come from Russia itself.

And as they return home, so grows the threat back home.

It's too early to say if there is a direct Syria connection to the St Petersburg attack.

But the very fact it will be high on the Russian security services' list of possibilities demonstrates the new dangers for ordinary Russians.

President Vladimir Putin's intervention in Syria may have been a strategic masterstroke, outflanking the West yet again.

But the airstrikes in distant Syria may well be sowing consequences for the cities and towns of Russia.

Topics: unrest-conflict-and-war, terrorism, world-politics, russian-federation