Russia has repeatedly accused Ukraine of carrying out drone strikes on its territory in recent months.
Russia’s defence ministry said three drones were downed in the country’s capital Moscow on 30 July, with two crashing into offices.
Although Ukraine hasn’t claimed responsibility for specific incidents, President Volodymyr Zelensky has said that attacks on Russian territory were an “inevitable, natural and absolutely fair process”.
How many drone attacks have there been in Russia?
According to Russian media reports monitored by BBC Verify, there have been more than 120 suspected drone attacks this year in Russia and Russian-controlled territory in Ukraine.
These have been concentrated in the Bryansk and Belgorod regions in Russia near the western border with Ukraine, as well as in Russian-annexed Crimea.
There have been a series of drone attacks in the Moscow region in recent months, which is about 450km (280 miles) from the border, including a wave of strikes on 30 May which damaged several buildings.
Flights were forced to be diverted from Vnukovo International Airport in Moscow after a drone attack on 4 July.
It was also shut briefly following the drone attacks on 30 July.
Russia accused Ukraine of trying to kill President Vladimir Putin in an alleged attack on his residence in the Kremlin on 3 May, which Kyiv denies.
Oil facilities, airfields and energy infrastructure have all been targeted in 2023.
We have identified at least nine reported drone attacks on oil depots. One of these was in Sevastopol, a major city in Crimea, which was hit on 29 April, destroying several of its oil tanks.
On 31 May, an oil refinery was set ablaze in Krasnodar Territory in southern Russia, about 200km (124 miles) from the Crimean border. The regional governor said it was probably caused by a drone.
Layla Guest, an analyst at Sibylline security consultancy, says: “Ukrainian forces will highly likely prioritise targeting oil refineries, as well as railway infrastructure and wider Russian logistics, to cause maximum disruption as part of their strategy ahead of the impending counter-offensive.”
In February, a drone crashed about 100 km (62 miles) from Moscow, in what the local governor said was an attempt to target civilian infrastructure.
A picture of the wreckage appeared to be consistent with a UJ-22 – a type of drone manufactured by Ukraine.
It has a range of 800km (497 miles) in autonomous flight. Its range under directly-controlled flight is much shorter.