Last week's blast in the pedestrian subway under Pushkin Square in the centre of Moscow came almost one year after a series of apartment bombings killed more than 300 people and ignited the second Chechen war, which is still nowhere near an end.
Ammonium nitrate is a fertiliser.
It is easy to acquire and anybody with knowledge of explosives can make a bomb from it. The death toll of last week's explosion has reached 11, with three victims dying days later in hospital. Ten casualties have been identified thus far. Meanwhile, the media is repeatedly broadcasting footage of the dead and the wounded. No surprise there.