KYIV, Ukraine (AP) — Russian forces over the weekend continued to shell Ukrainian cities amid a grinding push to seize more land in the east of the country, with Ukrainian officials saying that Moscow is having trouble launching its much-anticipated large-scale offensive there.

One person was killed and one more was wounded on Sunday morning by the shelling of Nikopol, a city in the southeastern Dnipropetrovsk region, Governor Serhii Lysak reported. The shelling damaged four residential buildings, a vocational school and a water treatment facility.

In Kharkiv, Ukraine’s second largest city, one person was wounded after three Russian S-300 missiles hit infrastructure facilities overnight, regional Governor Oleh Syniehubov said.

Ukrainian forces also downed five drones — four Shahed killer drones and one Orlan-10 reconnaissance drone — over the partially occupied Zaporizhzhia and Donetsk regions on Saturday evening, Kyiv’s military reported.

The attacks come as Russian forces push to take over more land in the eastern industrial heartland of Donbas, comprised of the Donetsk and Luhansk regions. Ukrainian and Western officials have warned that Russia could launch a new, broad offensive there to try to turn the tide of the conflict as the war approaches the one-year mark.

But Ukrainian officials say that Moscow is having trouble mounting such an offensive.

“They are having big problems with a big offensive,” Oleksiy Danilov, the secretary of Ukraine’s National Security and Defense Council, told Ukrainian television on Saturday night.

“They have begun their offensive, they’re just not saying they have, and our troops are repelling it very powerfully. The offensive that they planned is already gradually underway. But (it is) not the offensive they were counting on,” Danilov said.

A US-based think tank noted that it is also Russia’s pro-Kremlin military bloggers who question Moscow’s ability to launch a broad offensive in Ukraine. They “continue to appear demoralised at the Kremlin’s prospects for executing a major offensive,” the Institute for the Study of War said in its latest report.

Earlier this week the owner of the Russian Wagner Group private military contractor actively involved in the fighting in Ukraine said that the war could drag on for years.

Yevgeny Prigozhin said in a video interview released late Friday that it could take 18 months to two years for Russia to fully secure control of Donbas. He added that the war could go on for three years if Moscow decides to capture broader territories east of the Dnieper River.

The statement from Prigozhin, a millionaire who has close links to Russian President Vladimir Putin and was dubbed “Putin’s chef” for his lucrative Kremlin catering contracts, marked a recognition of the difficulties that the Kremlin has faced in the campaign, which it initially expected to wrap up within weeks when Russian troops invaded Ukraine on February 24.

Russia suffered a series of humiliating setbacks in the fall when the Ukrainian military launched successful counter offensives to reclaim broad swaths of territory in the east and the south.

On Sunday, Prigozhin said that Wagner fighters have taken over the Krasna Hora settlement north of Bakhmut, a strategic city at the epicentre of the fighting in recent months.