A senior Ukrainian prosecutor says the civilian death toll since the onset of Russia's invasion in February of last year has exceeded 10,000. But he adds that it is just the tip of the iceberg.

The prosecutor spoke in an interview with the Interfax-Ukraine News Agency on Wednesday.

The official said the invasion has left 10,749 civilians dead, including 499 children. But he said the actual figure will climb significantly as it remains difficult to confirm victim numbers in areas occupied by Russia.

Meanwhile, Ukraine and Russia appear to be intensifying their attacks using unmanned aerial vehicles.

The Ukrainian military said on Thursday that it shot down all 15 Iranian-made drones launched in an attack by Russia. Authorities in Ukraine's capital, Kyiv, said a drone strike took place for a second consecutive day.

The governor of Russia's Kaluga region, southwest of the capital, Moscow, said on Thursday that seven drones were intercepted over his region.

Russia's defense ministry accuses Ukraine of attempting to attack with the unmanned aircraft. It says the drones caused no casualties or structural damage.

This is the latest in a recent series of drone attacks in Russia. Multiple drones entered Moscow's business district on Tuesday and one of them crashed into a high-rise building, which had already been hit in a similar incident on Sunday.

Ukraine has not acknowledged its involvement in any of the drone strikes in Russia.

But a report in The New York Times said earlier this week that its analysis indicated that at least three different Ukrainian-made drones had been used in attacks inside Russia, including Moscow.