MOSCOW—

Russia's steady buildup of military forces along its border with Ukraine is raising concerns that Moscow, which annexed Crimea in 2014 and then began backing separatists in eastern Ukraine militarily — including with Russian troops — may be considering an overt military campaign against its southwestern neighbor.

Russian Defense Minister Sergei Shoigu said in televised remarks last week that the military had created four new divisions, nine brigades and 22 regiments since 2013 and deployed them in the Southern Military District, adjacent to southern Ukraine, as well as in Russia's restive North Caucasus region.

"In recent years, the military-political situation on the southwestern strategic direction has become more acute," Shoigu said in citing the rationale for Moscow's military buildup in the region. "Mainly, this is due to the growing military presence of NATO in eastern Europe, the situation in Ukraine and the activities of international terrorist groups, including in the North Caucasus."

In an interview with the newspaper Vedomosti, Russian military expert Ruslan Pukhov noted that along with reactivating the 1st Guards Tank Army in Russia's Western Military District, near its border with northern Ukraine, Moscow plans to form two other armored groups for deployment near the Ukrainian border.