North Korea's air force has conducted more training than normal this winter despite the death of leader Kim Jong-Il, a report said Tuesday.
The North's military drills for winter began in late November, showing no "abnormal" activities following Kim's death on December 17, the South's Yonhap news agency said.
"We, however, witness a slight increase in the number of air force flights taking part in training," an unnamed government official was quoted as saying.
The South will go ahead with its planned joint exercise with US troops in March as Pyongyang has not eased its tough stance towards Seoul, Yonhap said.
Kim's youngest son Jong-Un has visited army units as head of the armed forces in an attempt to burnish his military credentials.
Jong-Un, believed to be in his late 20s, was proclaimed supreme leader and appointed commander of the 1.2-million-strong military following the death of his father.
The new regime has vowed retaliation against Seoul for alleged disrespect during the mourning period for its late leader.
Cross-border tensions have been high since the South accused the North of torpedoing a warship with the loss of 46 lives in March 2010.
The North denied involvement but eight months later shelled an island near the tense Yellow Sea border and killed four South Koreans.