Russia may be temporarily easing its offensive in Ukraine as the country's military attempts to reassemble its forces for a renewed assault, analysts have said.

Russian forces made no claimed or assessed territorial gains in Ukraine on Wednesday "for the first time in 133 days of war", according to the Institute for the Study of War.

The think tank based in the US suggested that Moscow may be taking an "operational pause" that did not entail "the complete cessation of active hostilities".

"Russian forces will likely confine themselves to relatively small-scale offensive actions as they attempt to set conditions for more significant offensive operations and rebuild the combat power needed to attempt those more ambitious undertakings," the institute said.

Shelling continued in the east of Ukraine, where at least nine civilians were killed and six wounded in 24 hours, Ukrainian officials said.

Ukraine's presidential office said in its Thursday morning update that cities and villages in seven Ukrainian regions had been shelled in the past day. Most of the civilian deaths occurred in Donetsk province, where fighting was ongoing. Seven civilians were killed there, including a child, the presidential office said.

Ten cities and villages were shelled in Donetsk, and 35 buildings were destroyed, including a school, a vocational college and a hospital, officials added.

Donetsk is part of the Donbas, a mostly Russian-speaking industrial area where Ukraine's most experienced soldiers are concentrated. Pro-Russian separatists have fought Ukrainian forces and controlled much of the Donbas for eight years.

Russian president Vladimir Putin recognised the independence of two self-proclaimed republics there just before Russia invaded Ukraine on February 24.

Mr Putin claimed victory in Luhansk, the other province constituting the Donbas, on Monday after Ukrainian forces withdrew from the last city they controlled there.

The governor of Luhansk, Serhiy Haidai, denied on Wednesday that the Russians had completely captured the province.

A boarding school was hit, but no-one was injured, in Kharkiv - Ukraine's second-largest city.

The Kharkiv region, which lies along the border with Russia, is under daily shelling, and two civilians had been killed there over the past 24 hours.

The Ukrainian military said on Thursday that Russian forces had also carried out shelling and helicopter strikes in the Sumy region in the northeast.

Even as the fighting continued, the UK's Ministry of Defence (MoD) said it thought Russia's military was "reconstituting" its forces.

A ministry intelligence assessment issued on Thursday said the heavy shelling along the front line in Donetsk was likely to be intended to secure previous Russian gains.

The MoD noted a new law under consideration by the Russian parliament to give the government special economic powers amid the war.

The law would allow "Russia to avoid acknowledging it is engaged in a war or its failure to overcome Ukraine's military that was outnumbered and outgunned", the ministry said.