North Korea is believed to have deployed 50 submarines amid the ongoing crisis talks with neighbouring South Korea. Seoul reports suggest all the submarines are out of their bases.
"Seventy percent of North Korea's submarines left their bases, and their locations are not confirmed," an unnamed South Korean military official told reporters, according to Yonhap news agency.
Pyongyang is thought to possess 70 submarines and is reportedly working on developing submarine-based ballistic missile system.
The development has come when troops of the rival Koreas have been kept on high alert over the worsening situation despite talks. Pyongyang has also doubled the number of troops on the border. With the crisis further deteriorating in the Korean peninsula, high-ranking officials began to hold talks on Saturday, 22 August. The negotiations continued on Sunday in the truce village of Panmunjom.