Russian Defence Minister Sergei Shoigu said on Wednesday that the country needed to further develop its armed forces in the face of "increased NATO activity" on its borders.

"The difficult military and political situation in the world and the increased activity of NATO countries near the Russian borders require further quality development of the armed forces," Shoigu told officials in televised remarks.

Among the Russian armed forces' priorities are "increasing their effectiveness, maintaining the combat readiness of nuclear forces and strengthening the potential of non-nuclear deterrent forces," the defence minister added.

Western countries have this month raised the alarm over reported Russian military activity near Ukraine, with the US saying it has "real concerns" over a new troop build-up on the border.

Moscow has dismissed mounting Western claims that Russia may be preparing to invade Ukraine and says any military buildup is a response to growing NATO activity near its borders.

On Tuesday, Shoigu accused Washington of sending its bombers to practice a nuclear strike on Russia -- from the east and the west -- during its "Global Thunder" military exercises.

Renewed Western fears about Russia's plans in eastern Ukraine have come amid a clash over an unexpected migrant crisis on the border with Kremlin-aligned Belarus and EU member Poland.