There has been a couple of explosions on the Metro in Moscow, killing at least 37 people. The early indications are that these were deliberately triggered explosions, leading to suspicions that it was a terrorist attack.

At least 37 people have been killed in two suspected suicide bombings on the Moscow Metro system at the peak of the morning rush hour, officials have said.
The first blast occurred in the central Lubyanka station at 0756 (0356 GMT). Police said the dead included 14 people inside a train and 11 on the platform.
The second explosion came about 40 minutes later at the Park Kultury station, where 12 people were killed.

Metropolitan transport systems are entirely vulnerable to this kind of attack. The terror of travellers caught in such an incident doesn't bear thinking about.

My thoughts go out to the bereaved and the injured. I imagine we'll learn more during the day.