Ukraine has devastated a Russian command post in the Belgorod region bordering the country just one day after Vladimir Putin's nuclear threats.
Social media images show a huge mushroom cloud erupting in Russia, and Ukraine's intelligence service - the GUR - claimed responsibility for the strike.
It said: "Explosions and thick smoke - in the city of Gubkin, Russia, the command post of the 'Sever' troop group was hit.
"In the city of Gubkin, Belgorod Region, the command post of the 'Northern' troop group of the Russian occupation army was successfully hit.
"Inhabitants of Gubkin observed thick black smoke, smelled it, and heard loud explosions. GUR of the Ministry of Defense of Ukraine reminds - for every crime committed against the Ukrainian people, there will be an adequate, fair retribution."
Unconfirmed reports on Telegram also claimed drones also attacked the 13th GRAU arsenal in Russia's Novgorod region, near Kotovo hundreds of miles inside Russia.
According to a milblogger on the platform, projectiles for barrel artillery, mines for mortars, missiles for MLRS "Grad", "Smerch" and "Uragan", as well as "Iskander" missiles, Kndriv KN23 are kept
Anti-aircraft missiles up to S-300, S-400 and ammunition for the Tor complex are also said to be kept there.
It comes as US President Joe Biden approved provision of anti-personnel land mines to Ukraine, according to a US official, potentially handing Kyiv a major boost.
The development was reported by Reuters, citing a US official who spoke on condition of anonymity.
It's thought the move could help slow the advance of Putin's troops in the east of Ukraine, especially when used along with other munitions provided by Washington.
This Sunday, Russian unleashed a major assault on Ukraine's powergrid, with 120 missiles and 90 drones unleashed in "massive combined strike".
The following day Biden approved Ukraine's use of long-range missiles in Russia for the first time, though still with strict conditions.
Ukrainian media has said Kyiv has already used the US ATACMS rockets to strike inside Russia just as Vladimir Putin approved a new Russian nuclear doctrine.
Explosions were reportedly seen at an ammunition depot in Karachev, some 75 miles from the Ukrainian border, as Kyiv marked the 1000th day of the conflict to use the missiles in an offensive capacity for the first time on Tuesday.
The Kremlin has branded Biden’s decision to permit Ukraine to strike into Russia an “escalation” as it once more attempted to use its nuclear capabilities to intimidate Kyiv's Western allies.
Putin's spokesperson Dmitry Peskov said on Tuesday: "The Russian Federation reserves the right to use nuclear weapons in the event of aggression against it with the use of conventional weapons."
The Russian President has issued a decree allowing Russian nuclear weapons to be deployed against a non-nuclear force if it was backed up by a nuclear-armed nation - for example, Ukraine backed by the United States.
It follows months of warnings from the Kremlin that if the US allowed Ukraine to launch American, British and French missiles deep into Russia, Moscow would consider the NATO members directly involved in the conflict.
It had been understood that strikes in Russia would require US permission before launch and will predominately be targeted towards North Korean troops in Russia's Kursk region, as Russia pushes Kyiv's offensive there backwards.