KYIV (Reuters) -Advancing Ukrainian troops are facing "desperate resistance" from Russian forces around the eastern city of Bakhmut, and are inflicting big losses on Russian troops in the south, Ukrainian military chiefs said on Friday.

Reuters could not verify the battlefield situation. Russia has not officially acknowledged Ukrainian advances in the early stages of a counteroffensive, and said it had inflicted heavy losses on Kyiv's forces in the previous 24 hours.

Colonel General Oleksandr Syrskyi, who is in charge of Ukrainian ground forces, said the situation in the east was tense and Russia was bringing its best divisions into the Bakhmut sector with backup from artillery and aircraft.

"We continue to conduct offensive actions in separate directions, occupying dominant heights, and strips of forest with the aim of forcing the enemy gradually out of the outskirts of Bakhmut. Realising this, the enemy units put up desperate resistance," Syrskyi said on the Telegram messaging app.

The small, ruined city of Bakhmut has seen some of the fiercest and bloodiest fighting since Russia's full-scale invasion in February 2022. The Ukrainian military said last week it had started to push Russian forces back around Bakhmut.

Syrskyi said Ukrainian forces were also advancing in the south. Kyiv said on Thursday it had regained control of about 100 square km (38 square miles) of territory in just over a week of its counteroffensive against Russian forces.

Brigadier General Oleksandr Tarnavskyi, commander of Ukrainian troops in the southern Tavriia sector, said there had been 36 combat engagements and 578 attacks in the past 24 hours in the sector.

"The enemy's losses in killed and wounded amounted to more than four companies," he wrote on Telegram. A company typically consists of 100–250 soldiers.

(Reporting by Olena Harmash, Editing by Timothy Heritage)