National Aerospace Development Administration (NADA) * Academy of National Defence Science

Recent commercial satellite imagery indicates that North Korea preparing the Sohae Satellite Launching Station (“Tongchang-ri”) for launching of a new larger space launch vehicle. The Sohae gantry tower has been undergoing significant modifications. So will be increased the gantry about three sections of 46 m to 60 m (without crane) !
The rocket by a source is described "as a booster for a super ICBM or a heavy-lift space launcher. It is completely new from what they have done so far."
It could be a totally changed space launcher with 3 m diameter and new engines. But North Korea has not the know-how to develop new large engines. That can only mean that already exist the technical requirements for such a propulsion.

Uniformed NADA

2017, March 19 -- North Korea has successfully conducted the ground test of its new rocket engine in fully modus (still without the second combustor), added with four steering engines. According to the North Korean news agency KCNA, the test measured the thrust power in the combustion chamber, the structural safety and reliability of the engine, and the movement of the turbine.

2016, Sept. 20 -- North Korea has successfully conducted the ground test of a new rocket engine, the country's state news agency reported.
North Korean leader Kim Jong-Un visited the Sohae Space Center to guide the test of "a new type high-power engine of a carrier rocket for the geo-stationary satellite," the Korean Central News Agency (KCNA) said.
This test was “aimed to make a final confirmation of the feature of combustion chamber, operation accuracy of valves and control systems and structural reliability of the engine during 200 seconds-long working time". North Korea also says the engine has a thrust of
80 tons of force
! However, this refers to twin-combustor arrangement.

Note: What was previously just a guess, seems to be confirmed: North Korea has at least blueprints of an old Soviet ICBM engine. The new North Korean engine "Pektusan" is clearly comparable to an engine of the KB Glushko. Two combustors use a common turbopump. Typical is the low arrangement of the TP between the nozzles.
It is pointless to suggest that there is another engine. It is completely clear that there is a pair with a turbopump in the middle, mounted on a platform. Such engines has constructed only Glushko. North Korea have not the know-how to develop an engine of this magnitude itself.
The display (left) shows only one engine for the test. The lowered TP on the platform makes sense only when a second engine is added in future.

Meanwhile Ukraine's state space agency has cofirmed that the rocket engine "Pektusan"  is the same as the type of engine used by Ukraine-made space vehicles (UPI Aug. 16).

"Pektusan 80 tf liquid rocket" is written in red
Translated: Ju Shobo & Han Ho Seok

Engine arrangements in comparison