Seoul (dpa) - North Korean leader Kim Jong Un has called for "big efforts" to expand his country's military capabilities during the inspection of a newly built submarine, state media reported on Tuesday.

State news agency KCNA said Kim expressed his satisfaction with the vessel, which would soon be deployed in waters off the country's east coast.

The KCNA report did not specify the date or location of the inspection, nor did it provide details on the submarine.

South Korean media have speculated that the submarine could be a Sinpo class vessel capable of launching a ballistic missile, and that the report is meant to send a signal to US President Donald Trump.

During a brief meeting last month in the border village of Panmunjom between North and South Korea, Trump and Kim agreed to set up working groups to relaunch stalled talks on North Korea's nuclear weapons programmes and economic sanctions.

Last week, Pyongyang warned that a joint military exercise planned by the US and South Korea for next month could have potential consequences for those talks.

During the submarine inspection, Kim "stressed the need to steadily and reliably increase the national defence capability" by developing naval weapons and equipment, KCNA reported.