Ukraine has denied reports of a Russian military buildup near its eastern border, raising concerns about a new round of fighting with pro-Moscow separatists.

Recent social media videos show Russian military trains and truck convoys transporting tanks and missiles in the country’s southwest near the Ukrainian border.

Pentagon spokesman John Kirby told reporters on Monday that Washington was keeping an eye on the situation, and The Washington Post reported that US officials were concerned.

However, Ukraine’s defense ministry said late Monday that “no additional deployment” of Russian forces had been observed near the border.

The ministry stated that the released videos could be a “element of special informational and psychological actions” and depicted a planned troop movement following a Russian military exercise.

On Tuesday, Kremlin spokesman Dmitry Peskov dismissed reports of a possible build-up, saying there was no need to “waste time” on “low-quality” claims.

“The movement of our military equipment and army units… is solely our responsibility,” he told reporters. “No one has ever been threatened by Russia.”

The Ukrainian army is embroiled in a simmering conflict with pro-Russian separatists, which erupted following Moscow’s annexation of Crimea in 2014.

Following an increase in violence earlier this year, Russia amassed around 100,000 troops on Ukraine’s borders in March, raising fears of a major escalation in the conflict.

Under pressure from Kiev’s Western allies, Moscow announced a withdrawal, but both Ukraine and the US stated at the time that it was limited.

On Tuesday, Ukraine’s military announced that one of its soldiers had been killed in a separatist attack.

In the conflict, which has claimed over 13,000 lives, at least 59 Ukrainian soldiers have been killed since the beginning of the year, compared to 50 in all of 2020.

According to the separatists, 40 of their fighters have died.

Ukraine and its Western allies accuse Russia of sending troops and arms across the border to support the separatists, claims denied by Moscow.