Ukraine has denied reports of a Russian military buildup near its eastern border, which had raised fears of an escalation on the borders.

The Ukrainian statement came hours ahead of an announcement on the resignation of Defense Minister Andriy Taran, which reportedly came over his health situation.

Taran, 66, is yet to comment on his resignation, a decision that must be ratified by Parliament.

The top Ukrainian official had previously complained about his health, according to the leader of Ukrainian President Volodymyr Zelensky's parliamentary faction.

Pentagon Spokesperson John Kirby had alleged Monday that Washington was "monitoring the situation" on the eastern Ukrainian borders. The Washington Post quoted US officials as saying they were "concerned".

Ukraine denied these allegations, as its Ministry of Defense asserted that Kyiv did not observe any deployment of Russian forces.

Kremlin Spokesman Dmitry Peskov had dismissed the reports of a potential "buildup" on Tuesday, as he said there was no need "to waste time on low-quality claims."

"The movement of our military equipment and army units ... is exclusively our business," he told reporters. "Russia has never threatened anyone."