President Volodymyr Zelenskiy said on Thursday that Ukraine's military faced difficulties on front lines in the east and south of the country, but were dominant in their campaign.

Senior military officials reported Ukrainian gains in the east -- long the focal point of the 17-month-old conflict - around the shattered Russian-held city of Bakhmut.

Ukraine in June launched a counter-offensive in the east and in the south, where it hopes to advance to the Sea of Azov and sever a Russian land bridge between occupied parts of the east and the Crimean Peninsula, annexed by Moscow in 2014.

Russian accounts said Moscow's forces had repelled Ukrainian attacks near Bakhmut, farther north where fierce fighting has also flared and on the southern front.

In his nightly video address, Zelenskiy said Ukrainian forces faced fierce Russian resistance in all frontline sectors.

"There is heavy fighting. They are trying to stop our boys with all their strength. Very fierce attacks," Zelenskiy said, referring to Bakhmut and other centres in the east.

"In the south, everything is difficult. But whatever the enemy does, it is Ukrainian strength that dominates."

Zelenskiy said Russian drone attacks this week, including an assault on shipping infrastructure in the Danube port of Izmail, underscored the need for improved anti-aircraft defences.

"In all, the terrorists have deployed against Ukraine at least 1,961 (Iranian-made) shahed drones and we managed to down a significant number of them," he said.

"Unfortunately, not all of them. We are working on downing more of them -- downing a maximum. We are working so that there will be more anti-aircraft systems."

General Oleksandr Syrskyi, commander of Ukrainian land forces, said he was meeting officers in the east to speed up Ukraine's advances -- which Zelenskiy and other officials ackowledge have been slower than they wished.

"In the Bakhmut sector, my work is devoted to current problems of accelerating the pace of the advance, the prospects for greater activity and resolution of issues that interfere with the implementation of tasks," Syrskyi wrote on Telegram.

Serhiy Cherevatyi, a spokesman for the eastern group of Ukrainian forces, said Kyiv's troops were advancing "consistently and relentlessly" on the fringes of Bakhmut, captured by Russian troops in May after months of battles.

"Every day we are talking about hundreds of metres and over the week about kilometres," Cherevatyi said in comments reported by Ukrainian media.

Russia's Defence Ministry said its forces had thwarted eight Ukrainian attempts to advance near Bakhmut and nearby areas. Two Ukrainian attacks were countered near Lyman and Svatove farther north and attempted advances in the south were also stopped.

(by Ron Popeski and Oleksandr Kozhukhar; Editing by Leslie Adler and Cynthia Osterman)