The British Ministry of Defence reported this on Twitter.
British intelligence notes that since about February 15, there have not been any reports of Russian use of Iranian drones. Prior to that, the Ukrainian Armed Forces reported shooting down at least 24 Shahed-136 UAVs between late January and early February 2023, and scores were destroyed in the first few days of 2023.
"The lack of deployment of attack drones likely indicates that Russia has run down its current stocks. Russia will likely seek a resupply. Although the weapons do not have a good record in destroying their intended targets, Russia likely sees them as useful decoys which can divert Ukrainian air defense from more effective Russian cruise missiles," the British intelligence concluded.
On February 17, Ukraine’s General Staff reported that a new team of instructors from Iran had arrived in occupied Luhansk to train Russians to use attack drones.