KYIV (Reuters) -Kyiv reported a "complicated" situation in fighting in eastern Ukraine on Tuesday, and Moscow said its troops had advanced in the direction of the city of Kupiansk in the northeast.

Russia and Ukraine differed in their accounts of the latest battles since Kyiv launched a counteroffensive early last month, but both sides signalled that fighting was fierce.

The TASS news agency quoted the Russian defence ministry as saying its forces had advanced by up to 2 km (1.2 miles) in the direction of Kupiansk, an important railway junction in the Kharkiv region.

General Oleksandr Syrskyi, commander of Ukrainian ground forces, had said earlier on Tuesday that Russia had concentrated forces in the Kupiansk sector but that Ukrainian troops were holding them back.

"The situation is complicated but under control (in the east)," Syrskyi said on the Telegram messaging app.

Ukrainian officials have increasingly pointed to an intensification of Russian military activity near Kupiansk and nearby Lyman in the northeast. Both cities were retaken by Ukraine late last year and Lyman is also a railway junction.

Reuters was unable to verify the situation on the battlefield.

Since Kyiv launched its counteroffensive in early June, aided by weapons supplied by its Western allies, it has taken back more than 210 square kilometres (81 square miles) of land, Deputy Defence Minister Hanna Maliar said on Monday.

But Russia still holds vast swathes of territory following its full-scale invasion in February 2022, and Ukrainian troops have encountered heavily defended positions and minefields.

Russian President Vladimir Putin has said the counteroffensive is "not succeeding", and Russia has been trying to break through Ukrainian lines as Kyiv's forces attack. Ukraine says it is advancing slowly to avoid high casualties.

A spokesperson for Ukraine's troops in the east told a briefing that Russian forces were trying to seize the initiative in the Lyman-Kupiansk direction, but also said Kyiv's forces were holding them back.

Ukraine's military say Russia has more than 100,000 troops and more than 900 tanks in the area.

Russian troops were also continuing to send reserves to the Bakhmut sector in eastern Ukraine to try to stop Ukrainian forces advancing, Syrskyi said.

Ukrainian troops have taken a cluster of villages in the south since starting the counteroffensive, and a military spokesperson said they were entrenching after advancing.

The spokesperson reported heavy fighting for the settlement of Staromayorske southwest of the city of Donetsk, and said Ukrainian troops had the advantage there.

(Reporting by Anna Pruchnicka, Editing by Timothy Heritage and Bernadette Baum)