Ukrainian President Volodymyr Zelensky suggested on Sunday that plans for Kyiv's long-awaited counteroffensive last year had been leaked to Russia ahead of time.

Ukraine's counteroffensive in 2023, powered by billions of dollars in Western arms, largely fell flat, failing to break through multiple lines of Russian defences and fortifications.

"Our counteroffensive action plans were on the Kremlin's table before the counteroffensive actions began," Zelensky said Sunday at a press conference in Kyiv.

His office subsequently confirmed to AFP that Zelensky was referring to Moscow obtaining sensitive military planning information.

Zelensky did not provide any other details on the leak.

He went on to say that Kyiv was preparing "several" versions of its battlefield strategy for 2024 to help avoid a repeat.

Asked whether Ukraine had plans for another attempt at a counteroffensive this year, he said: "We have a plan, a clear plan. Several plans will be prepared because of information leaks."

Russian forces are now back on the advance across eastern Ukraine, having captured the symbolic frontline town of Avdiivka and seeking to press their advantage in ammunition and manpower.