Russia has begun its “big revenge” for Ukraine’s resistance to its invasion, Ukrainian President Volodymyr Zelenskyy has said, as Russian forces claimed a series of incremental gains in his country’s east.

Zelenskyy has been warning for weeks that Moscow aims to step up its assault on Ukraine after about two months of virtual stalemate along the front line that stretches across the south and east.

While there was no sign of a broader new offensive on Monday, the administrator of Russian-controlled parts of Ukraine’s eastern Donetsk province, Denis Pushilin, said Russian troops had secured a foothold in Vuhledar, a coal mining town whose ruins have been a Ukrainian bastion since the outset of the war.

Pushilin’s adviser, Yan Gagin, said fighters from Russian mercenary force Wagner had taken partial control of a supply road leading to Bakhmut, a city that has been the focus of a Russian offensive for months.

A day earlier, the head of Wagner said his fighters had secured Blahodatne, a village just north of Bakhmut.

Kyiv said it had repelled assaults on Blahodatne and Vuhledar. The Reuters news agency could not independently verify the situations there, but the locations of the reported fighting indicated clear, though gradual, Russian gains.

Zelenskyy said Russian attacks in the east were relentless despite heavy casualties on the Russian side, casting them as payback for Ukraine’s success in pushing Russian forces back from the capital, northeast and south earlier in the conflict.

“I think that Russia really wants its big revenge. I think they have [already] started it,” Zelenskyy said.

“Every day they either bring in more of their regular troops, or we see an increase in the number of Wagnerites,” he told reporters in Ukraine’s southern port city of Odesa.

Vuhledar sits south of Bakhmut, near where the eastern front line protects Russian-controlled rail lines supplying Moscow’s forces in southern Ukraine. Mykola Salamakha, a Ukrainian colonel and military analyst, told Ukrainian Radio NV that Moscow’s assault there was coming at a huge cost.

“The town is on an upland and an extremely strong defensive hub has been created there,” he said. “This is a repetition of the situation in Bakhmut — one wave of Russian troops after another crushed by the Ukrainian armed forces.”

Weapons deliveries months away

In recent weeks, Western countries have pledged hundreds of modern tanks and armoured vehicles to equip Ukrainian forces for an offensive to recapture territory later in 2023.

But the delivery of those weapons is months away, leaving Kyiv to fight on through the winter in what both sides have described as a meat grinder of relentless attritional warfare.

Moscow’s Wagner mercenary force has sent thousands of convicts recruited from Russian prisons into battle around Bakhmut, buying time for Russia’s regular military to reconstitute units with hundreds of thousands of reservists.

Zelenskyy is urging the West to hasten delivery of its promised weapons so Ukraine can go on the offensive.

Kremlin spokesperson Dmitry Peskov said Western countries supplying arms leads “to NATO countries more and more becoming directly involved in the conflict — but it doesn’t have the potential to change the course of events and will not do so”.

The US-based Institute for the Study of War think tank said “the West’s failure to provide the necessary materiel” last year was the main reason Kyiv’s advances had halted since November.

That had allowed Russia to apply pressure at Bakhmut and fortify the front against a future Ukrainian counterattack, its researchers said in a report, though they said Ukraine could still recapture territory once the promised weapons arrive.

Zelenskyy met Danish Prime Minister Mette Frederiksen on Monday in Mykolaiv, a rare visit by a foreign leader close to the front. The city, where Russia’s advance in the south was halted, had been under relentless bombardment until Ukraine pushed the front line back in November.

Zelenskyy’s office released footage of the president greeting Frederiksen with a handshake on a snowy street before entering a hospital where they met wounded soldiers.

Iran raid

While Kyiv has secured weapons from the West, Moscow has turned to allies, including Iran, which Kyiv and the West say has provided Russia with hundreds of long-range so-called “suicide drones” used to attack Ukrainian cities.

Over the weekend, an Iranian military factory was hit by a drone attack that a US official said appeared to have been carried out by Israel. Israel has not commented.

Kyiv implied that the attack on Iran was payback for Tehran’s military support for Russia: “Explosive night in Iran,” senior Zelenskyy aide Mykhailo Podolyak tweeted. “Did warn you.”

Iran summoned the charge d’affaires at Ukraine’s embassy over Podolyak’s remarks. Russia said the raid on Iran “could have unpredictable consequences for peace and stability in the Middle East”.

Unlike many Western countries, Israel has stopped short of openly arming Kyiv, but it is seen as alarmed by Russia’s reliance on Iranian drone technology it views as a regional security threat.

Ukraine, which has received large supplies of uncrewed aerial vehicles (UAVs) from its partners, said it planned to spend nearly $550m on drones this year, with 16 supply deals signed with Ukrainian manufacturers.

France, meanwhile, said it had agreed with Australia to cooperate to manufacture “several thousand” shells for Ukraine.

Russia’s invasion, which it launched on February 24 last year claiming it was necessary to protect itself from its neighbour’s ties with the West, has killed tens of thousands of people and driven millions from their homes.