SEOUL, March 7 (UPI) -- North Korea has hacked into the smartphones of key Seoul government officials and has launched a cyberattack against South Korea's rail operator.
As Pyongyang vowed a "nuclear strike" in response to joint military exercises, Seoul's spy agency said the South's networks are still vulnerable to computer breaches, Yonhap reported.
North Korea had warned in February that hacking of computer devices would be a response to unilateral sanctions that culminated in the shutdown of the Kaesong Industrial Complex in February.
In a recent statement, South Korean President Park Geun-hye said the North has not stopped provocations in cyberspace, and its acts of cyberterrorism could cause economic havoc and threaten national security.
North Korea has previously hacked into a South Korean agricultural cooperative bank in 2011 and attacked three South Korean television networks and a bank in March 2013.
The attacks are becoming more sophisticated, and Seoul's National Intelligence Service said a fresh round of attacks attempted to infiltrate the state rail operator and the digital phones of South Korean officials.
The NIS, however, did not say whether the information on the smartphones was compromised.
The agency is to hold an emergency meeting on Tuesday, and said the attacks were confirmed to be of North Korean origin, and the attack on the rail operator, which occurred on Feb. 18, has heightened network security at KORAIL.
A South Korean cyber crisis alert has been raised to "Caution" in the wake of recent attacks.