SEOUL  - North Korean leader Kim Jong-Un has replaced his defence chief with a hawkish general in a shakeup apparently aimed at tightening his grip over the military, a report said Thursday. Vice Marshal Kim Jong-Gak was sacked as defence minister after just seven months in office, Yonhap News Agency quoted an unnamed senior South Korean presidential official as saying. He was replaced by Kim Kyok-Sik, a hawkish general believed to have orchestrated the North’s sinking of a South Korean warship and an artillery attack on a border island in 2010, it said.