SEOUL (Reuters) - South Korea and the United States will begin their annual joint military drills on Monday, South Korea's Yonhap news agency reported on Sunday, citing the Joint Chiefs of Staff (JCS).

       South Korea and the United States regularly stage military exercises, mainly in the spring and summer, but North Korea has for decades reacted angrily, calling them a rehearsal for war.

       The exercises followed last week's preliminary drills and will continue for nine days, Yonhap said, citing the JCS.

       The JCS and Seoul's defence ministry did not immediately respond to Reuters requests for comment.

       A day after the allies kicked off preliminary training, North Korea did not answer routine calls on inter-Korean hotlines which had only just been reactivated after the North severed them a year ago amid strained ties.

       Kim Yo Jong, the powerful sister of North Korean leader Kim Jong Un, accused the South of "perfidious behaviour" for going ahead with the exercises.

       (Reporting by Hyonhee Shin; Editing by Christopher Cushing)