Explosion heard near center of Kyiv.

A loud explosion was heard near the center of Kyiv overnight on Dec.

16, Kyiv Independent journalists report. Kyiv Mayor Vitali Klitschko said that air defense is working and warned resident to stay in bomb shelters. Just one hour prior, Ukraine's air force warned a Russian drone was heading to Kyiv from the Boryspil region.

Russia has stepped up targeting of critical energy infrastructure in Kyiv using missiles and drones as winter sets in.

Earlier on Dec.

15, Ukraine's air force warned it detected groups of UAVs launched from the Zaporizhzhia Oblast, partially under Russian occupation.

Klitschko later confirmed that explosions occurred in the Podil area of Kyiv.