North Korea is believed to have started rebuilding a rocket launch site it had pledged to dismantle.
The secretive state began dismantling the long-range rocket site at Sohae last summer after Kim Jong Un held his first talks with Donald Trump last year.
It was seen as a significant gesture from Pyongyang amid cooling tensions between North Korea and the US.
However, satellite images shared by the Beyond Parallel website suggest the site is now being restored.
Monitors say the commercial satellite imagery is from March 2nd - only two days after the second summit between Kim and Trump was cut short without a deal on denuclearisation.
The images show construction cranes and vehicles, as well as other indicators of renewed activity.
North Korea experts Joseph Bermudez and Victor Cha explained: "This renewed activity... may indicate North Korean plans to demonstrate resolve in the face of US rejection of North Korea’s demands at the summit to lift five UN Security Council sanctions enacted in 2016-2017.
"This facility had been dormant since August 2018, indicating the current activity is deliberate and purposeful."
Donald Trump claimed that talks last week had collapsed as North Korea wanted crippling international sanctions "lifted in their entirety".
He told reporters: "They were willing to denuke a large portion of the areas that we wanted, but we couldn’t give up all of the sanctions for that."
That was disputed by North Korean officials, who insisted they'd only asked for partial sanction relief in return for closing some of its nuclear sites.
