We will use your email address only for sending you newsletters. Please see our Privacy Notice for details of your data protection rights.

Sign up fornow and never miss the top politics stories again.

The Russian leader expressed his condolences and said a terror attack would be considered "first of all".

Mr Putin, who was in St Petersburg for a meeting with Belarussian leader Alexander Lukashenko, said: "The causes of this event have not been determined yet, so it’s too early to talk about possible causes.

"The investigation will show. Certainly, we will consider all variants, common, criminal, first of all, of a terrorist nature.