[HIGHLIGHTS] Kremlin drone explosion Russia "US directed, Ukraine attack"

The Russian president's office says the attack was carried out by U.S. drones.

The U.N. says it is investigating the incident. The Russian government says it has no evidence of the attack being carried out in its territory. The attack comes as Russian troops are accused of shooting down a Ukrainian helicopter with a U.K.-made drone. The Ukrainian government says the drone was shot down by a Russian-made drone that was fired from a Ukrainian military base in the east of the country.