Russia launched a drone strike on the Ukrainian capital Kyiv early on Wednesday, wounding at least six people and damaging buildings in two districts, city officials said. Explosions boomed across the morning sky as Ukraine's air force warned of drones approaching the city and Mayor Vitali Klitschko said air defences were repelling an enemy attack.

Early indications suggest a Russian anti-aircraft system may have downed the passenger jet that crashed in Kazakhstan, a US official told CNN, as authorities recovered a second black box that they hope will shed light on the cause of the disaster that killed dozens of people.