Ukraine says it has destroyed a sophisticated Russian air defence system in occupied Crimea.
Kyiv’s security service (SBU) and navy carried out the attack on a Russian facility near Yevpatoriya using cruise missiles and drones, a Ukrainian intelligence source told the BBC.
Video footage on social media showed a fire and smoke near the city, in the west of the Russian-occupied peninsula.
Moscow has yet to directly comment on the claim.
Instead, the Russian defence ministry said it had shot down several Ukrainian aerial drones and thwarted a separate attack on a naval patrol vessel.
Earlier on Thursday, a number of explosions were reported in the Crimean peninsula, which Russia illegally occupied in 2014.
According to the BBC’s intelligence source, the Ukrainian operation used drones to take out radar equipment, then cruise missiles to hit air defence missile launchers.
“After disabling the radar stations, the navy units hit the S300 and S400 ‘Triumph’ systems, worth $1.2bn, by two Neptune cruise missiles,” the source said.
Neptune missiles were designed by Ukraine’s military for naval use but have been modified for ground targets as well.
No details were provided on the number of the batteries that had been hit.
Citing local residents, Ukrainian media reported that explosions happened at around 05:40 local time (02:40 GMT) and smoke was seen near the military base.
BBC Verify has analysed footage on social media of smoke rising and believes it to be of the attack on Yevpatoriya.
Russia’s ministry of defence, on the other hand, downplayed the importance of the attack and said that they shot down 11 drones over Crimea.
Russian-appointed local officials have not reported any damage in the military facility or the air defence systems.
The S400 air defence system has been in service since 2007, and is an upgraded version of the Cold War-era S300.
The most up-to-date version’s missiles can travel 400km (250 miles) and operate and attack targets at altitudes of 48km (30 miles).
The S400 can destroy aircraft and ballistic missiles.
Ukraine appears to be stepping up it operations on occupying forces in Crimea.
It launched a major attack yesterday on the port of Sevastopol, the headquarters of Russia’s Black Sea fleet.
Ukrainian officials claim that two Russian naval ships sustained serious damage.
Russian officials said 10 missiles were used in the attack, which reportedly left 24 people injured. The use of the missiles served to demonstrate Ukraine’s increased use of long-range munitions.
Meanwhile, Ukraine’s finance ministry said on Thursday that the country would receive $1.25bn (about £1bn) from the United States as part of the World Bank’s PEACE in Ukraine project.
Officials said the funds would be used for non-military purposes and would be directed towards vulnerable groups and for the provision of educational and medical services.