Recent satellite imagery indicates new activity at the test stand of North Korea's main submarine-launched ballistic missile development shipyard in a move that suggests the communist nation is planning to accelerate its SLBM program, a website monitoring the North said Thursday.

The April 29 imagery of the Sinpo South Shipyard shows a heavy-lift crane with its stabilizer legs deployed and boom extended out over the test stand's service tower, and a 13-meter-long flatbed truck adjacent to it on the access road, 38 North said.

The test stand was used during 2014-2016 for launch systems verification, and pop-up and prototype testing of the Pukguksong-1 (KN-11) submarine-launched ballistic missile (SLBM), it said.

It is difficult to determine from the imagery alone whether the activity is related to maintenance, removal of the service tower or preparations for an upcoming test, 38 North said.

The new activity comes after the February test launch of a Pukguksong-2, which is the land-based version of the Pukguksong-1 SLBM and two tests of the KN-17 medium-range ballistic missile (MRBM) on April 5 and 16, 38 North said.

In conjunction with these developments, the recent activity at the Sinpo test stand likely has a number of implications for the future of the SLBM program and suggests that North Korea is planning to accelerate the program or develop new designs to complement its land-based ballistic missiles," it said. (Yonhap)