(Reuters) - A Russian official said on Monday that fighting was gripping parts of Ukraine's northeastern Kharkiv region which Moscow has been trying to seize and added that Ukraine's military was pouring men and equipment into the contested area.

Ukrainian President Voldodymyr Zelenskiy said Kyiv's forces were gradually pushing Russian troops out of the contested area. His top commander predicted that Moscow would try to press forward pending the arrival in Ukraine of sophisticated Western equipment, including U.S-made F-16 fighter jets.

Russian forces crossed into parts of Kharkiv region last month and officials say they have seized about a dozen villages.

Vitaly Ganchev, Russia-appointed governor of the areas of Kharkiv region controlled by Moscow, said Russian forces were beating back Ukraine's latest counter-attacks in areas near Vovchansk, five kilometres (three miles) inside the border.

"There is fighting still going on in the Kharkiv sector. The fiercest clashes are in Vovchansk and near Lyptsy," Ganchev told Russian news agencies.

"The enemy is sending reserves and trying to counter-attack but is meeting a fierce response from our armed forces."

Russian President Vladimir Putin said the incursion sought to create a "buffer zone" to prevent Ukraine from shelling border areas, including Belgorod region, opposite Kharkiv.

Over the past week, Ukrainian officials have said the Russian advance is firmly under control.

Zelenskiy, in his nightly video address, said Ukrainian troops were "gradually pushing the occupiers out of the Kharkiv region". The military's General Staff reported 10 Russian attacks were repelled near Vovchansk and Lyptsi.

Ukraine's top military commander, Oleksander Syrskyi, said on Telegram that Moscow's commanders "were building intensity and expanding the geography of military activity.

"The enemy clearly understands that the gradual arrival of weapons and equipment from our partners, the arrival of the first F-16s, strengthens our air defences," he wrote. "Time is one our side and their chances of success will diminish."

Ukrainian military bloggers said Kyiv's forces were holding positions around Vovchansk and trying to break through Russian lines to consolidate units around the town.

Russian forces seized much of Kharkiv region in the early weeks of the February 2022 invasion, but Ukraine recaptured large swathes of territory later that year.

Kharkiv, Ukraine's second largest city, 30 km (18 miles) from the border, stayed out of Russian hands, and months of Russian attacks have eased, Ukrainian officials say, thanks to the arrival of new weaponry.

(Reporting by Ron Popeski and Oleksander Kozhukhar; Editing by Bill Berkrot)