South Korea said on Wednesday it had scrambled fighter jets in response to Russian military aircraft entering its air defence zone, the second such incursion in weeks.The relationship between the countries has worsened since South Korea joined Western sanctions following Russia’s invasion of Ukraine, and since Moscow built stronger ties with North Korea.Seoul’s defence ministry said multiple Russian aircraft had entered and then left its air defence identification zone over the East Sea, also called the Sea of Japan.“South Korea’s military detected the Russian aircraft before they entered the zone and deployed Air Force fighter jets to prepare for any contingency,” it said, without giving details.The Russian aircraft did not violate South Korean airspace, it said.F-15K fighter jets from South Korea’s air force fly above the Osan Air Base during the Invincible Shield exercise in Pyeongtaek on November 8, 2016. Photo: EPA-EFEAn air defence identification zone is not sovereign airspace but a buffer area where countries require foreign aircraft to identify themselves for security purposes.