KYIV, Ukraine - Ukrainian President Volodymyr Zelensky said on Tuesday Russia was increasing its attacks across the front line, as Kyiv called for the West to boost weapons supplies ahead of winter.

Neither side has made any significant territorial gain for months, but both Zelensky and the Kremlin have denied the conflict has ground to a stalemate.

"The military reported an increase in the number of enemy assaults," Zelensky said in a post on social media, with Russians attacking around the cities of Donetsk, Kupyansk and Avdiivka.

Zelensky has warned Russia is likely to increase air strikes against Ukraine's energy infrastructure ahead of the winter, as it did this time last year.

He called strikes on the city of Kherson a day earlier that killed three people and wounded a dozen -- including a newborn baby -- "revenge" attacks that were were "without any military necessity".

Andriy Yermak, Zelensky's chief of staff, met US Secretary of State Antony Blinken in Washington on Monday to press Ukraine's need to keep the flow of Western weapons coming.

"As winter approaches, we expect the Russian missile terror to intensify," Yermak posted on Telegram after the meeting.

"Therefore, we are in dire need of air and missile defence systems that will protect Ukrainian cities, key critical infrastructure facilities, and grain corridor routes," he said.

Yermak later said he also met US national security adviser Jake Sullivan as well as British and European security and foreign policy advisers to discuss the "situation on the battlefield".

Yermak said Russia has increased the number of its forces in Ukraine and that Kyiv "needs to maintain international support".

With the conflict dragging for almost 21 months, Ukraine fears growing Western fatigue and world attention on the Israel-Hamas war could weaken support for its army.