By Vitalii Hnidyi, Ivan Lyubysh-Kirdey and Yuliia Dysa
NEAR VOVCHANSK, Ukraine (Reuters) -Ukraine's military said on Tuesday its forces pulled back to new positions in two areas of the northeastern Kharkiv region where Moscow is pressing an offensive, and warned of a Russian force buildup to the north near its Sumy region.
A cross-border attack on a new flank in Sumy region would likely stretch Kyiv's depleted defenders even further after Russia's incursion into Kharkiv region opened a new front on Friday, forcing Ukraine to rush in reinforcements.
Russia has made inroads into the north of Kharkiv region and said on Tuesday it had taken a 10th border village, Buhruvatka. The police chief in Vovchansk, a town 5 kilometres (3 miles) from the border that has been the target of one of the main Russian thrusts, reported exchanges of fire in the north of the town.
"In certain sectors in the area of Lukyantsi and Vovchansk, units have moved to more advantageous positions as a consequence of enemy fire and storming action and in order to preserve the lives of our servicemen and avoid losses," the General Staff said in a statement late on Tuesday.
Regional governor Oleh Syniehubov said two people had been killed in shelling there. More than 7,500 people from Vovchansk and nearby border areas had been evacuated.
"For five days we never left the house, we didn't see anyone, we were so afraid to go out we never even opened the door," Natalia Yurchenko, who was evacuated from Vovchansk, told Reuters.
Apart from the devastation and the blow to Ukrainian morale in the region, home to Ukraine's second largest city of Kharkiv, the incursion is a distraction for Kyiv's defensive operations in the east where Russia has focused its offensive for months.
Military spy chief Kyrylo Budanov said Moscow had already committed all the troops it had in the border areas for the Kharkiv operation, but that it had other reserve forces that he expected to be used in the coming days.
"As of yesterday evening, a rapid trend towards a stabilisation of the situation had emerged - that is, the enemy is, in principle, already blocked at the lines that it was able to reach," he said in televised comments.
Top Ukrainian officials say they do not believe Russia has the troop numbers to capture the city of Kharkiv.
Russia was maintaining the tempo of its attacks in the region, according to data compiled by the Ukrainian General Staff which said there had been 14 Russian assaults so far on Tuesday, compared with 13 on Monday and 22 the day before.
Budanov described the situation as fluid and rapidly changing, saying the "active phase" of the Russian operation was still under way.
TEST OF MANPOWER
Budanov said Russia had small groups of forces in the border areas near Ukraine's Sumy region in the vicinity of the Russian town of Sudzha from where Russian natural gas transits into Ukraine by pipe on its way to European customers.
"As for the Sumy region, the Russians actually planned an operation in the Sumy region from the very beginning... but the situation did not allow them to take active actions and start the operation," he said.
The Russian assault is a test of Ukrainian manpower, which military analysts say is running short and needs to be replenished.
That shortfall is compounded by months of delays in vital U.S. military aid, some of which Secretary of State Antony Blinken said during a trip to Kyiv on Tuesday had finally arrived, with more on the way that would "make a real difference".
Emil Kastehelmi, an open-source intelligence analyst with Black Bird Group, told Reuters the most important battle in the Russian push was taking place in Vovchansk, some 45 kilometres from the city of Kharkiv.
"If Russia wants to go further south, Vovchansk needs to be captured. In this town, Ukraine is putting up a fight, and it seems that stronger Ukrainian defences are starting to appear around 6-8 km from the border in other places too," he said.
Tamaz Gambarashvili, head of Vovchansk's military administration, said in televised comments that the town was "almost destroyed".
"It's completely under (Kyiv's) control, but there are small groups that try to enter the outskirts of the city, so there is a shooting battle," he said.
Liz Throssell, spokesperson for the UN High Commissioner for Human Rights, said her office was "deeply concerned" at the plight of civilians in Kharkiv region where she said at least eight people had been killed and 35 injured since Friday.