Ukraine's military claimed Thursday that 800 Russian soldiers were killed in the past day, mostly in fighting in the eastern Donetsk region.

Giving its regular morning roundup of the fighting, Ukraine's military said Russian forces were focused on an offensive in the Bakhmut sector and its attacks in the Avdiivka and Kupiansk sectors were unsuccessful.

It said more than 800 Russian soldiers, one aircraft, a helicopter and three tanks were destroyed over the past day.

It also reported an unspecified number of civilian casualties as a result of Russian air, missile and rocket attacks on the largely ruined, Ukrainian-held city of Bakhmut and two other cities in the Donetsk region – Kostiantynivka and Kurakhove.

Russia denies targeting civilians in what it calls its "special military operation" in Ukraine. Reuters could not independently verify battlefield accounts.

Meanwhile, Ukrainian and Russian troops battled in eastern regions Thursday as Kyiv tried to push back occupying forces.

President Volodymyr Zelenskyy urged the West to provide his army with heavy tanks to boost their firepower.

The Ukrainian military said the Russians were focused on an offensive in the Bakhmut sector of the Donetsk region, but their attacks in the Avdiivka and Kupiansk sectors were unsuccessful.

The governor of the neighboring Luhansk region, meanwhile, said Ukrainian troops were recapturing areas there "step-by-step" but cautioned it was "not happening fast."

Luhansk and Donetsk make up the Donbass region, Ukraine's industrial heartland, parts of which were seized by Russian-backed proxies in 2014.

Russia declared Donetsk, Luhansk, Kherson and Zaporizhzhia regions as part of its territory in September after referendums condemned by Ukraine and Western countries. Russia does not fully control any of the four regions.

Bakhmut, which is now largely in ruins after months of battering by Russian artillery, is important because the Russian leadership wants to have a success to hold up to the Russian public after a series of setbacks in the war.

It is located on a strategic supply line between the Donetsk and Luhansk regions. Gaining control of the city, with a pre-war population of 70,000-80,000 that has shrunk to close to 10,000, could give Russia a stepping stone to advance on two bigger cities – Kramatorsk and Sloviansk.

Heavy weapons

A senior U.S. administration official meanwhile predicted a long road ahead in the war that has now raged for nearly 11 months.

"The fighting is still quite hot (in Donetsk) ... what we're seeing in Bakhmut we should expect to see elsewhere along the front, that there will be continued fighting in the coming months," the official said in Washington on Wednesday.

In his evening video address on Wednesday, Zelenskyy urged Western allies to provide his army with tanks and heavy weapons to combat the Russian forces.

French President Emmanuel Macron said Wednesday his government would send light AMX-10 RC armored combat vehicles to help its war effort.

Zelenskyy thanked Macron but said: "There is no rational reason why Ukraine has not yet been supplied with Western tanks."

The Ukrainian leader also said his troops outside Bakhmut were inflicting numerous losses on their adversaries and Russia was building up its forces in the region.

Appeal for tanks

As the war grinds on, the Kyiv government has repeatedly asked Western allies for heavier fighting vehicles such as the Abrams and German-made Leopard tanks.

U.S. President Joe Biden said Wednesday the United States was considering sending Bradley Fighting Vehicles to Ukraine. The Bradley has a powerful gun and has been a U.S. Army staple to carry troops since the mid-1980s.

Biden's decision, however, would fall short of sending the Abrams tanks that Ukraine has sought.

The United States is preparing another package of weapons, which could be announced in the coming days on top of about $21.3 billion in security assistance so far to Ukraine.

The United States has increased the capability of the weapons it has sent including shoulder-fired Stinger anti-aircraft missiles as well as Javelin anti-tank missiles, the HIMARS rocket system and NASAMS surface-to-air missiles.

During a visit by Zelenskyy to Washington last month, the United States pledged to send the Patriot missile system to repel Russian missile and drone attacks.

Russia launched its invasion on Feb. 24, citing threats to its security and a need to protect Russian speakers. Ukraine and its allies accuse Russia of an unprovoked war to seize territory.