Photo taken on April 4, 2017 shows both the Russian national flag (L) and the flag of St. Petersburg with black ribbons in tribute to the victims of a blast in St.Petersburg metro, on a building in St. Petersburg, Russia. The bombing in the subway system in St. Petersburg on Monday has killed 14 people, Russian Health Minister Veronika Skvortsova said Tuesday. (Xinhua/Irina Motina)
