Surveillance satellite footage from the United States shows a 'dramatic' rise in rail movement along North Korea's border with Russia.

Friday, a U.S. observer reported that this week's satellite imagery revealed a "dramatic" increase in rail traffic along the North Korean-Russian border, prompting concerns about potential arms transfers following the summit between the two countries last month.

Beyond Parallel, a project of the Center for Strategic and International Studies in Washington, D.C., reported a "unprecedented" number of freight rai....