By Dan Peleschuk
KYIV, June 3 (Reuters) - Russia is pummeling major Ukrainian cities in an effort to sustain a sputtering war effort marked by a struggle to maintain momentum on the battlefield, where advances over the last month slowed to a near halt, researchers say.
Tuesday's devastating air attacks on Ukraine - which killed 23 people and wounded more than 130 - followed months of stalling progress for Moscow, which has faced stiffer Ukrainian resistance on the ground and mounting strikes on oil
infrastructure and military-industrial sites from the air.
While Russian forces are still grinding forward in parts of Ukraine's eastern region of Donetsk, their glacial pace - combined with pushback elsewhere on the front line - threatens to weaken the Kremlin's hand in any future peace talks, analysts say.
President Vladimir Putin has insisted that the war cannot end unless Russia controls all of Donbas - which groups the Ukrainian regions of Donetsk and Luhansk. Ukrainian forces still hold around a fifth of Donetsk.
"In the broader picture, if the Russians can't find ways to pick up momentum significantly, the goal of capturing Donbas this year is slipping out of their reach fast," said John Helin, analyst and co-founder of the Black Bird Group, a Finnish conflict-analysis team.
According to Black Bird Group's latest data, shared with Reuters, Russian forces captured just 82 square km of Ukrainian territory in May, compared to 94 square km in April and 25 square km in March.
That stands in stark contrast to the much larger gains made over the same period last year, when Moscow's troops took 538 square km, 226 square km, 185 square km, respectively, according to Black Bird.
The Institute for the Study of War (ISW), a Washington-based think tank, said a series of escalating Russian strikes on Kyiv and other cities in recent weeks has been aimed partly at distracting from Moscow's battlefield woes and the impact of Ukraine's own long-range attacks inside Russia.
On Wednesday, Ukrainian drones struck an oil export terminal in St Petersburg, hours before a major annual economic forum kicked off in the city, in a bid to embarrass the Kremlin.
"Putin is using massive strike packages against Kyiv in an effort to break Ukraine's will to fight as well as to disguise his weakness," ISW said in an assessment on Tuesday, following the attack on Kyiv and Dnipro, a southeastern industrial hub.
It was the third heavy assault on the Ukrainian capital within a month.
Russia's defence ministry did not respond to a request for comment for this story. Putin has said his forces were advancing on the battlefield and could soon conclude the war.
The Kremlin said on Wednesday it would continue striking Ukraine "systematically" in response to attacks like those on St Petersburg.
SLOW PACE OF GAINS
The Kremlin's spring offensive has primarily targeted Ukraine's so-called "fortress belt" of strategic cities in Donbas, stretching from Slovyansk and Kramatorsk in the north to Kostiantynivka in the south.
Kyiv has vehemently refused to cede the remaining parts of Donbas that Russia has been unable to conquer in four years of war. And analysts say Moscow's slower rate of advance means it is losing leverage.
A drone-infested "kill zone" along the 1,200-km front line, in which territory is fiercely contested and weakly controlled, makes concrete losses and advances difficult to assess. The front line is often blurred into a "grey zone", with small pockets of troops from both sides intermingled across several kilometers.
Earlier this week, Ukrainian open-source group DeepState said Russian troops in May saw their smallest monthly gains since October 2023 - 14 square km - despite a 37.5% spike in assaults by Russian forces.
It added that a delay in showing Ukrainian advances meant Kyiv's forces were likely to have retaken more territory than Russia captured for the first time since a failed Ukrainian counteroffensive in 2023.
DeepState's map shows Ukraine made minor new gains in May around the village of Novoselivka, some 50 km southwest of Pokrovsk, compounding earlier gains near the same area after a successful winter counterattack.
"The war is entering a new stage and it is important for the Ukrainian state not to lose the initiative," the group said on Monday.
A senior Ukrainian commander, Brigadier General Andriy Biletsky, who commands Ukraine's Third Army Corps, told Reuters last month that Ukraine had a six-month opportunity to knock Russia onto the back foot and strengthen its own hand for peace talks.
Mathieu Boulègue of the U.S.-based Center for European Policy Analysis said Moscow's war machine is also grappling with shrinking industrial capacity due to Western sanctions, as well as dwindling stocks of nearly all weaponry.
"They are really slowly, I think, changing the cost-benefit calculus of the Kremlin," he said of Russia's appetite for continuing the war.
(Reporting by Dan Peleschuk)
