Kyiv military officials said on Monday that Russia has bulked up its forces around the devastated city of Bakhmut in eastern Ukraine and has switched its troops from defense to offense, but Ukraine has been preparing to repel the attacks.
Russia captured Bakhmut, theater of some of the bloodiest fighting of the 20-month-old war, in May. Ukraine launched a counteroffensive in June aimed at retaking occupied land in the country's south and east, including Bakhmut.
"In the Bakhmut area, the enemy has significantly strengthened its grouping and switched from defense to active actions," General Oleksandr Syrskyi, Ukraine's commander of ground forces, wrote on Telegram.
Volodymyr Fityo, head of communications for Ukraine's ground forces command, said Russian forces had been preparing since early this month to retake positions around Bakhmut lost during the Ukrainian counteroffensive.
"We saw this, the intelligence reported everything. We had been preparing, strengthening our defensive positions, engineering fortifications and pulling up reserves," Fityo told Reuters by telephone. "This does not come as a surprise for us."
Both men said Russian forces were particularly active near the Ukrainian-held town of Kupiansk in the northeast, where Fityo said Russia had numerical superiority.
Reuters could not independently verify accounts on the battlefield.
In its nightly report, the Ukrainian General Staff said Kyiv's forces remained on the offensive near Bakhmut.
"The enemy unsuccessfully tried to restore lost positions near Klishchiivka," it said, referring to a village south of Bakhmut recaptured by Ukraine in September.
Russian troops also tried to advance in Synkivka, north of Kupiansk, but made no headway, it added.
Russia has also been concentrating much of its efforts in recent weeks on a bid to encircle and capture Avdiivka, a strategic town southwest of Bakhmut.