President Volodymyr Zelenskiy called for faster construction of fortifications in key sectors under pressure from Russian forces, particularly in eastern Ukraine, the focal point of Moscow's advances 21 months into its invasion.
He issued his appeal after touring Ukrainian positions in the northeast, one of several areas where Russian forces have been trying to make recent headway - and recapture areas taken back by Ukrainian troops a year ago. He said one of the meetings he held with commanders dealt with fortifications.
"In all major sectors where reinforcement is needed, there should be a boost and an acceleration in the construction of structures," Zelenskiy said in his nightly video address.
"This, of course, means the greatest attention to the Avdiivka, Maryinka and other sectors in Donetsk region. In Kharkiv region, this means the Kupiansk sector and the Kupiansk-Lyman line."
Russia has made slow progress in trying to secure all of the eastern regions of Donetsk and Luhansk, but has boosted attacks in several areas. These include Kupiansk near Kharkiv, retaken by Ukraine in a drive through the northeast a year ago.
Russian occupying forces have built solid fortifications and minefields of their own in areas they have held since pouring over the border in February 2022.
Those defences have been a key factor in holding back a Ukrainian counteroffensive under way since June. Ukrainian troops have made only incremental gains in the east and south.
Russian forces have focused attention since mid-October on the devastated town of Avdiivka, known for its vast coking plant and its position as a gateway to the Russian-held regional centre of Donetsk, 20 km (12 miles) to the east.
Military spokesperson Oleksandr Shtupun said Ukrainian forces had rebuffed Russian attacks on the coking plant.
"The plant is under our control. The enemy is suffering significant losses there," Shtupun told Espreso TV, noting Russian artillery and air attacks inside and around the town.
"The Russians are actively pressing ground attacks, sometimes using armoured vehicles."
Reuters could not verify accounts of fighting from either side.
Avdiivka was briefly seized by Russian-financed separatists who took control of large stretches of eastern Ukraine in 2014. It has held out since thanks to a considerable extent to fortifications put in place by its Ukrainian defenders.
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