Russia said on Thursday a division of its S-400 missile defense system would take part in a military drill in Serbia, underlining Moscow's wish to keep a traditional ally on side even as Belgrade pursues links with NATO and the European Union.

It will be the first time that the sophisticated S-400s, together with a Pantsir missile battery, will be participating in military exercises abroad, Moscow's Defense Ministry said in a statement.

For its part, Serbia's Defense Ministry said the exercises — dubbed Slavic Shield 2019, aimed to simulate the "use of a joint (combat) group... in defending... against enemy reconnaissance and offensive actions."

"Apart from anti-aircraft missile systems in use in the Serbian army, missile systems that are in use by the Russian Air Force will also be used" in the live-fire exercise set to run until Oct. 29, it said in a statement.

The exercises began on Wednesday but were not made public until Thursday.