Several weeks had passed without a strike using a Shahed drone being reported.
But more than a dozen were reported to have been shot down by Ukrainian forces earlier this week.
In its latest intelligence update, the Ministry of Defence in London said: “For the first time in three weeks, there have been reports of attacks by Iranian-provided one-way attack (OWA) uncrewed aerial vehicles (UAVs).
“These events remain to be verified, but it is likely that Russia exhausted its previous stock of several hundred Shahed-131s and 136s and has now received a resupply.”
Going into more detail, the briefing added: “On 06 December 2022, the Ukrainian General Staff reported shooting down 17 UAVs, including 14 Shahed-136s. On 07 December 2022, Ukrainian officials reported the use of Iranian-provided OWA UAVs targeting Zaporizhzhia and Dnipro oblasts (provinces).
“The last previously reported shooting down of Iranian Shahed-136s in Ukraine was on 17 November 2022. If verified, it is likely that Russia has recommenced attacks with newly delivered OWA UAV systems.”
Ukrainian officials said Russian forces have shelled the entire frontline of the Donetsk province in eastern Ukraine.
They said it showed the Kremlin had scaled back its ambitions to secure only the bulk of Ukrainian lands it has claimed as Russian.
The fiercest fighting occurred near the towns of Bakhmut and Avdiivka, the region’s governor Pavlo Kyrylenko said on TV.
He added that artillery hit the town of Toretsk, southwest of Bakhmut, killing one civilian and damaging 12 buildings.
He said "the entire front line is being shelled" and Russian troops were also trying to advance near Lyman, which was recaptured by Ukrainian forces in November.
Ukrainian forces countered with barrages from rocket launchers in Bakhmut and other parts of the Donetsk area that neighbours Luhansk province, according to reports.
Ukraine’s military command said Russian artillery attacked civilian infrastructure in the towns of Kupiansk and Zolochiv in the northeastern region of Kharkiv and Ochakiv in the Mykolaiv area.
Ukrainian anti-aircraft downed several of the missiles aimed at the Kharkiv region, governor Oleh Synyehubov said on Telegram.
Putin’s generals have ordered an onslaught against key infrastructure sites in Ukraine, including electricity power stations, to plunge millions of home into cold and darkness, as winter tightens its grip on the country.
The attacks targeting essential services for civilians are likely to amount to a war crime, according to western officials.
They have been launched as Putin’s military campaign in Ukraine flounders, with his troops having had to retreat from the southern city of Kherson and facing other counter-offensives.
Around 40,000 civilians are believed to have been killed in Putin’s war which started on February 24, with 100,000 Russian soldiers estimated to have died or been wounded, with a similar casualty level for the Ukrainian military.