KYIV, Feb 1 (Reuters) - The situation on the front lines in eastern Ukraine has become tougher as Russian forces step up an offensive, President Volodymyr Zelenskiy said on Wednesday in another gloomy military assessment from Kyiv.

Russia has gained momentum on the battlefield, announcing advances north and south of the city of Bakhmut, its main target for months. Locations of reported fighting clearly indicate incremental Russian advances.

"A definite increase has been noted in the offensive operations of the occupiers on the front in the east of our country. The situation has become tougher," Zelenskiy said in a evening video address.

Zelenskiy said the Russians were trying to make gains that they could show on the first anniversary of the war on Feb 24.

Deputy Defence Minister Hanna Malyar earlier said fierce fighting continued in eastern Ukraine, where Russian troops are trying to gain ground near the strategic logistics hub of Lyman.

Malyar, writing on the Telegram messaging app, said despite heavy losses the Russians were also pressing ahead with an offensive near the towns of Bakhmut and Avdiivka.

Russian forces were driven out of Lyman in October.

"Fierce fighting rages in the east. The enemy is trying to expand the area of its offensive in the Lyman sector. It is making powerful attempts to break through our defences," said Malyar, adding that Ukrainian forces were holding out against an opponent that had more troops and weapons.

"Despite heavy losses, the Russian invaders are also continuing their offensive in the Bakhmut, Avdiivka, and Novopavlivka sectors," she said.