South Korea says it fired warning shots after Russian military planes entered its airspace.
Fighter jets were also scrambled in response.
According to the Defence Ministry in Seoul, it's the first time an aircraft from Moscow has violated the country's territorial sky.
It is planning to summon officials from the Russian Embassy to register formal protests.

Israeli strikes kill 26 in Gaza, health officials say
US government starts likely brief shutdown as House fails to approve deal
Thousands demonstrate in Minnesota and across US to protest ICE
France tightens infant milk rules after recalls
