11 June 2024 (Lloyd's List) - SOME 60 merchant ships were impacted by GPS jamming off the South Korean coast over a week-long period at the end of May into early June, according to Lloyd’s List Intelligence vessel-tracking data.

South Korea’s joint chiefs of staff claimed North Korea was interfering with GPS signals for several days last month, according to reports from local media.

Evidence of disruption emerged in Automatic Identification System data on May 28.

That day nine vessels were impacted with AIS signals erroneously showing them near the Northern Limit Line, a maritime boundary between South and North Korea. The latter disputes the validity of the line.

Some vessels, such as the Greece-flagged VLCC Maran Leo (IMO: 9602473) (green arrow in graphic below), were anchored at Pyeongtaek anchorage when their AIS signal was disrupted.

GPS jamming also impacted vessels sailing to the South Korean ports of Daesan/Seosan and Pyeongtaek.

Sixty cargo-carrying vessels experienced disruptions to their AIS between May 28 and June 2.

Efforts to jam radio signals were most intense on June 2 with 41 different ships showing up near the NLL, according to Lloyd’s List Intelligence vessel-tracking data.

Analysis of historical AIS data shows no vessels falsely appearing in this specific area since at least the start of 2023.

The occurrence of GPS jamming coincides with escalating tensions between North and South Korea.

South Korea also reported consecutive days of jamming efforts in March this year.

The interference of GPS signals is not a new tactic for Pyongyang, but prior to March the last reports of these attacks occurred in 2016.