A canister containing an alkaline substance exploded on a tram in the Russian capital on Sunday, injuring at least five people, Moscow police said. Ambulances arrived at the site in the Lefortovo region of northeast Moscow, a duty officer said. Russia's Interfax news agency reported that medical helicopters had airlifted some of the injured to the Sklifosovsky Burn Center. The injured were being treated for chemical and acid injuries, Interfax said, citing unidentified police officers at the scene. It was not immediately clear what caused the canister to explode. A series of deadly explosions blamed on Chechen rebels in recent...