Both the Russian and Ukrainian armies have staged rival combat drills in and near the Black Sea on Wednesday as both countries and their allies are on edge over accusations coming from the West of a major Russian troop build-up readying for an offensive on eastern Ukraine, which the Kremlin is vehemently denying. Ukraine's military days ago said a Russian offensive could come as early as January.

"Russia staged military drills in the Black Sea, south of Ukraine, on Wednesday and said it needed to sharpen the combat-readiness of its conventional and nuclear forces because of heightened NATO activity near its borders," Reuters reports of the new combat maneuvers.

AP archive image: Ukrainian helicopters fly over a Russian warship during Sea Breeze 2021 maneuvers last July.

The drills were described by the Russian defense ministry as featuring fighter jets and naval ships repelling air assaults on naval bases on the black Sea, as well as countering with offensive strikes on mock enemy targets.

Defense Minister Sergei Shoigu was cited as saying of the fresh drills meant to send a tough message not only to Kiev but to Washington and NATO that heightened military readiness in the region is needed due to "the complicated military and political conditions in the world and the growing activity of NATO countries near Russia's borders".

In particular the Russian defense ministry had on Tuesday described that the US had engaged in mock nuclear runs against Russia as a target. He said "this month, during US strategic forces exercise Global Thunder, ten strategic bombers practiced the option of using nuclear weapons against Russia almost simultaneously from the Western and Eastern directions."

And on Ukraine's side, it's defense leaders earlier detailed of ongoing drills:

The drills involved airborne troops and armored personnel carriers and ​simulated an attack on an enemy target, Ukraine’s defense ministry said Monday. The ministry’s statement was accompanied by footage showing the landing of troops supported by helicopters and other aircraft.

Growing NATO military activity and flights have also been observed in relation to the EU standoff with the Alexander Lukashenko government of Belarus over the migrant crisis at the Polish border.

All of this muscle-flexing stems mostly from earlier allegations from both US and Ukrainian government officials of a major Russian troop build-up near the Ukrainian border, though the Kremlin has countered that it's able to maneuver its troops within Russia's own sovereign borders and it doesn't mean anything threatening toward neighbors. As Reuters notes further, the accusations have grown more and more specific over the past week:

The head of Ukraine's military intelligence told the Military Times outlet this weekend that Russia had more than 92,000 troops massed around Ukraine's borders and was preparing for an attack by the end of January or beginning of February.

The Kremlin has lambasted the charge as a "smokescreen", with a recent official statement from spokesman Dmitry Peskov saying the US and its allies are likely trying to "camouflage aggressive intentions in Kyiv to try to solve the problem of the southeast by force."

Alarmingly, on Tuesday Russia's defense ministry informed China that NATO's military posturing over Ukraine and increased US nuclear-capable bomber flights over eastern Europe is a serious threat to China too.