A Ukrainian town, Kyiv, on Saturday staged a major drone attack on the Russian city of Kazan, 1,000 kilometres (620 miles) from the frontier.
It was gathered that this is the latest in a series of escalating aerial attacks in the nearly three-year conflict.
Local officials said the drone smashed into a high-rise apartment building in the city of more than 1.3 million, damaging a skyscraper but leaving no victims.
So far, the attacks into Russian territory are rare, Kazan and the surrounding oil-rich region of Tatarstan have previously been targeted by Ukrainian drones.
Such strikes are seen as embarrassing for Russia, almost three years into its military offensive on Ukraine.
Confirming the attack in a post on Telegram, the head of Tatarstan, Rustam Minnikhanov, said Kazan suffered a massive drone attack.
โWhile before industrial enterprises were attacked, now the enemy attacks civilians in the morning,โ he added.
Videos on Russian social media networks showed drones hitting a high-rise building and setting off fireballs.
According to the Foreign Ministry spokeswoman, Maria Zakharova, two drones hit a 37-storey apartment block.
She said Ukraine had been targeting an unspecified industrial facility, but that it suffered no damage.
