Ukraine’s troops have been forced to make a tactical retreat from three villages in the embattled east, the country’s army chief has said.

Col Gen Oleksandr Syrskyi warned of a worsening battlefield situation as Ukrainian forces wait for much-needed arms from a huge US aid package to reach combat zones.

He reported that Russian forces continue to attack “along the entire front line” of more than 620 miles, with pitched battles raging west of Avdiivka, the eastern city they took in February after a gruelling, months-long fight.

“The most difficult situation is in the Pokrovsk and Kurakhove directions, where fierce battles continue,” Col Gen Syrskyi’s said in an update posted to the Telegram messaging app, referencing two Ukrainian-held cities in the war-torn Donetsk region, once a hub of industry.

He added: “The enemy has engaged up to four brigades in these directions, is trying to develop an offensive west of Avdiivka and Marinka, making its way to Pokrovsk and Kurakhove.

“Units of the Defence Forces of Ukraine, preserving the lives and health of our defenders, moved to new frontiers west of Berdychi, Semenivka and Novomykhailivka.”

Two of these front-line villages lie less than 31 miles east of Pokrovsk, while the third is located around 20 miles by road from Kurakhove.

A Washington-based think tank predicted late on Saturday that Russian forces “will likely make significant tactical gains in the coming weeks” as acute ammunition shortages continue to hobble Ukraine’s defence efforts.

In its latest operational assessment, the Institute for the Study of War said that Moscow’s forces have opportunities to push forward around Avdiivka, and also threaten nearby Chasiv Yar.

Its capture would give Russia control of a hilltop from which it can attack other key cities forming the backbone of Ukraine’s eastern defences.

Despite this, the think tank assessed that neither of these efforts by Moscow are likely to cause Kyiv’s defensive lines to collapse “in the near term”.

The Russian defence ministry has confirmed that Moscow’s troops had taken a village about 10 miles north of Avdiivka, days after the war institute reported on its likely capture early on Thursday.

That day’s assessment described Moscow’s gains as “relatively quick but still relatively marginal”, adding that Russian troops had advanced by no more than three miles over the previous week.

US President Joe Biden promised on Wednesday that American weapons shipments would begin making their way into Ukraine within hours, as he signed into law a 95 billion dollar (£76 million) measure – 61 billion dollars (£48 billion) of which was allocated for Ukraine — that also included assistance for Israel, Taiwan and other global hot spots.

The announcement marked an end to the long, painful battle with Republicans in US congress over urgently needed assistance for Ukraine.

Elsewhere, Russian drones struck the Ukrainian Black Sea city of Mykolaiv early on Sunday, setting a hotel ablaze and damaging infrastructure, according to local officials.

Vitaliy Kim, the governor of Ukraine’s southern Mykolaiv province, said that the drones “seriously damaged” a hotel in its namesake capital, sparking a fire that was later extinguished.

Mr Kim also reported that the strike damaged heat-generating infrastructure in the city. He added that there were no casualties.

Russian state agency RIA reported that the strike on Mykolaiv targeted a shipyard where naval drones are assembled, as well as a hotel housing “English-speaking mercenaries” who have fought for Kyiv.

The RIA report cited Sergei Lebedev, described as a coordinator of local pro-Moscow guerrillas.

Also on Sunday morning, the Russian defence ministry said that 17 Ukrainian drones were downed overnight over four regions in the country’s southwest. Three drones were intercepted near an oil depot in Lyudinovo, an industrial town about 140 miles north of the Ukrainian border, governor Vladislav Shapsha said.

One of the Ukrainian drones damaged communications infrastructure in Russia’s southern Belgorod province, which borders Ukraine, governor Vyachaslav Gladkov said later on Sunday. There were no immediate reports of casualties.

The Russian defence ministry claimed on Sunday that its forces had destroyed ammunition depots and military equipment housed at three airports across Ukraine, including assault drones stored at Kamyanka Airfield in the country’s east.

The ministry’s online update said the attacks took place over the last 24 hours. There was no immediate comment from Kyiv.

Russian shelling on Saturday and overnight wounded at least seven civilians across Ukraine, according to Ukrainian officials.

A 36-year-old woman was pulled alive from the rubble after Russian shells on Sunday morning destroyed her home in the north-eastern Kharkiv region, the local administration reported.

Her 52-year-old neighbour was also rushed to a hospital with a stomach wound, the administration said.