The Ukrainian army said on Thursday it had partially halted a Russian advance in the northeast, where Moscow has secured its largest territorial gains in 18 months over the last week.
Moscow launched a major ground assault across the border into the Kharkiv region last week, a surprise move that has further stretched Ukraine's outgunned and outmanned forces.
Russian troops captured 278 square kilometres (107 square miles) of Ukrainian territory between May 9 and 15, mostly in the Kharkiv area, AFP has calculated using data from the Institute for the Study of War (ISW).
That is the largest territorial gain in a single operation since mid-December 2022, when Moscow advanced in the eastern Lugansk region.
Ukraine President Volodymyr Zelensky met military leaders in Kharkiv city on Thursday and said the situation was "very difficult" but "under control".
Kyiv meanwhile said it had managed to halt advancing Russian forces in some places.
"The situation in the Kharkiv sector remains complicated but is evolving in a dynamic manner," army spokesman Nazar Voloshin said on state TV on Thursday.
"Our defence forces have partially stabilised the situation. The advance of the enemy in certain zones and localities has been halted," he added.
In a daily briefing, Ukraine's General Staff said its forces had "significantly reduced the activity of the Russian occupiers."
"But the enemy is still trying to create the conditions for further advances," Voloshin warned.
Most of Russia's recent gains came in the Kharkiv area, though they have also claimed to have captured territory in the eastern Donetsk and southern Zaporizhzhia regions.
Following months of stalemate on the sprawling front lines, Russia has seized the initiative on the battlefield, pushing on from the capture of industrial hub Avdiivka in February.
Russian President Vladimir Putin said Wednesday his troops were advancing on "all fronts."
Some military analysts say Moscow may be trying to force Ukraine to divert troops from other hot spots, such as around the strategic town of Chasiv Yar in the Donetsk region.
Russia's defence ministry said Wednesday its forces had captured the symbolic village of Robotyne in the Zaporizhzhia region, some 300 kilometres (185 miles) south of Moscow's new offensive.
The settlement was one of the few successes for Kyiv of an underwhelming Ukrainian counter-offensive last summer.
The intensification of Russian attacks on multiple fronts has underscored the acute ammunition and manpower shortages crippling the Ukrainian military.
In the Kharkiv region, Ukraine has been forced to evacuate around 8,800 people since Russia launched the new assault, Kharkiv Governor Oleg Synegubov said Thursday.
Ukraine's SBU security service also said it had arrested an 18-year old Kharkiv resident who it alleged had provided information to Russia's rival FSB security agency to help the advance.
It said the man had been caught "red-handed" while "collecting information about army units defending the city. The occupiers needed this information to plan a new offensive in the Kharkiv region."
The country has also introduced several rounds of emergency power cuts this week, with its battered energy system unable to deal with a cold snap.
"Due to the shortage of electricity after Russian attacks, restrictions and emergency power cuts have been applied to consumers. More restrictions and cuts are possible today," the energy ministry said in a statement Thursday.
Moscow has destroyed several Ukrainian power plants in recent months in some of its largest aerial attacks on the country's energy grid throughout the 27-month war.
In China for a two-day state visit on Thursday, Putin said he was "grateful" to Beijing for "the initiatives they are putting forward to resolve" the war.
There are no indications Moscow and Kyiv are prepared to engage in direct talks, which Ukraine says would only be used by Russia to buy time to prepare for a new assault.
