The Russian military has started another round of ground and air exercises near its borders with Ukraine, in an apparent response to the growing political unrest in the east of the country.
Russian Defence Minister Sergei Shoigu was quoted by RIA Novosti as saying: "Starting today, exercises [involving] battalion tactical groups from the southern and western military districts will begin near the borders with Ukraine."
According to the minister, the troops will hold marching rehearsals and exercise deployments for performing assigned tasks.
"We are forced to react to such a development in the situation," Shoigu added, noting that the 'aircraft will do fly-bys close to the state border'.
The exercises come after Ukrainian security forces killed at least five pro-Russian activists at three checkpoints surrounding the city of Sloviansk, in an effort to assert control in the east.
Condemning the Ukrainian actions, Russian President Vladimir Putin said the deployment of military forces by the Ukraine Government was a crime against its own people and will have 'consequences'.
"That is simply a punitive measure that will without question have consequences for the people making these decisions, including for our inter-governmental relations," Putin said.
Meanwhile, the Ukrainian Foreign Ministry has issued a 48-hour deadline for Moscow to explain its military drills.
"Pursuant to provisions of the Vienna document on trust-building measures and security, Ukraine has issued a request to Russia through the Organization for Security and Cooperation in Europe (OSCE) to provide explanations for the objectives and place of the military exercise, the date on which it is expected to wind up, as well as the number and the types of army unity involved in them," the ministry said.
Russia, which already warned Ukraine of retaliation against an attack on its citizens, has also started a seven-day naval exercise in the Caspian Sea, involving ten naval vessels and 400 crew members, the Guardian reports.