South Korea summoned the Russian ambassador on Friday as tensions rise with North Korea. South Korean Vice Foreign Minister Kim Hong Kyun called in Russian Ambassador Georgy Zinoviev to protest the recently announced deal between Russian President Vladimir Putin and his North Korean counterpart Kim Jong Un. They urged Moscow to immediately call off its alleged military cooperation with Pyongyang. Earlier on Friday, Kim Yo Jung – the powerful sister of the North Korean leader – issued a vague threat of retaliation against South Korea. The threat came after South Korean activists flew balloons c…