British defence experts believe Russia is using a new supply of Iranian kamikaze drones after exhausting its stocks last month.
For the first time in three weeks, Ukraine has reported attacks by Iran-sourced one-way unmanned aerial vehicles (UAVs), according to an intelligence update from the UK’s Ministry of Defence (MoD).
It is understood that Russia had run through its Shahed 136 unmanned aerial vehicles more than two weeks ago after launching an estimated 400 drones.
The kamikaze aircraft led to a new bombing campaign on Kyiv and other Ukrainian cities when the Tehran-supplied UAVs were unleashed in October, flying over urban areas before nosediving and detonating their 40kg warheads.
Ukrainian general staff reported shooting down 17 UAVs on December 6, and officials said drones were used the following day to target the regions of Zaporizhzhia and Dnipro.
The MoD emphasised that the events have yet to be verified, but it is likely that Russia had exhausted its previous stocks and has now received a new supply.
The UK has pledged a £50 million ($61 million) package of defence aid comprising 125 anti-aircraft guns and technology to help Ukraine counter Iran-supplied drones, including radar and anti-drone equipment.
Britain has also sanctioned Iranian individuals and companies linked to the supply of the UAVs.
Russian forces, meanwhile, shelled the entire front line in the Donetsk region in eastern Ukraine, Ukrainian officials said, part of what appears to be the Kremlin's scaled-back ambition to secure only the bulk of territory it has claimed.
The fiercest fighting was near the towns of Bakhmut and Avdiivka, according to the region's governor, Pavlo Kyrylenko. Five civilians were killed and two wounded in Ukrainian-controlled parts of Donetsk over the previous day, he said on Friday.
"The entire front line is being shelled," he said, adding that Russian troops were also trying to advance near Lyman, which was recaptured by Ukrainian forces in November, one of numerous battlefield setbacks suffered by Russia in the past few months.
The comments came as American basketball star Brittney Griner landed in the US after being freed from Russia in a prisoner exchange.
She was arrested in Russia in February on drug charges and was freed in exchange for Russian citizen Viktor Bout, a convicted arms dealer jailed in the US.
The UAE and Saudi Arabia played a central role in her release and were thanked by US President Joe Biden and Secretary of State Antony Blinken.
It is a reminder that Moscow maintains lines of communication with the West despite the war, although the Kremlin said on Friday that the prisoner swap should not be seen as a step towards improving ties between Moscow and Washington, saying they were "in a sorry state".
War aims changed?
President Vladimir Putin has given conflicting statements on the goals of the war but is now clear the aims include some expansion of Russia's borders. This contrasts with comments at the start of Russia's "special military operation" in February, when he said his plans did not include occupying Ukrainian land.
Mr Putin on Friday repeated his accusation that the West was exploiting Ukraine and using its people as "cannon fodder" in a conflict with Russia, and said the West's desire to maintain its global dominance was increasing the risks of conflict.
"They deliberately multiply chaos and aggravate the international situation," Mr Putin said in a video message to a summit of defence ministers from the Shanghai Co-operation Organisation and a group of former Soviet states.
The Kremlin said on Thursday it was set on securing at least the bulk of the territories in east and south Ukraine, but appeared to give up on seizing other land in the west and north-east that Ukraine has recaptured.
Russia announced in October that it had annexed four provinces shortly after holding so-called referendums that were rejected as bogus and illegal by Ukraine, the West and most countries at the United Nations.
While Russia made clear it wanted to take full control of Donetsk and Luhansk ― two largely Russian-speaking regions collectively known as the Donbas ― it left unclear how much of the regions of Zaporizhzhia and Kherson it was annexing.
Ukrainian President Volodymyr Zelenskyy says his troops will eventually drive Russia from all captured territory, including the Crimea Peninsula annexed by Russia in 2014.