Where have North Korean troops been seen in Russia?
While North Korea has been supplying weapons to Russia for some time, the arrival of troops is a major escalation in its involvement in the war of Ukraine.
The first official evidence of large numbers of North Korean troops entering Russia was provided by the South Korean government, who last week published a press release outlining the increasingly close military cooperation between the two states.
According to the press release, an initial contingent of 1,500 North Korean special forces troops were transported on Russian naval ships to the port city of Vladivostok.
The South Koreans provided two high-resolution satellite images showing what they say are these troops in two sites in Russia.
The first shows a crowd of what the South Korean government estimates is 400 people assembled in an open space within a Russian military site close to the town of Ussuriysk, 98 kilometres north of Vladivostok.
The second image shows a smaller number of people, which the South Korean government state are around 250 North Korean soldiers.
This image was captured further north than the first. It shows an area that appears to be a military site close to the city of Khabarovsk in the Russian far east.
Footage circulating online
Amid reports of North Koreans entering Russia, several videos circulated widely.
While Sky News cannot confirm they show North Korean troops, one shows a group of soldiers of east Asian appearance. The person filming the video states they are North Korean, referring to them as 'allies'.
This video has been geolocated by Sky News to the town of Sergeyevka in the Russian far east.
A second video filmed nearby shows a group of soldiers training in a field at the same site.
Filmed from over a wall, the footage is too grainy to allow the soldiers to be identified visually, however, many have claimed it shows North Korean troops.
A third video, released by the Ukrainian government, shows troops being equipped. While it is not possible to geolocate this footage, the presence of boxes marked in Russian has been cited as evidence this shows North Korean troops in Russia.
What satellite images can tell us
While currently available videos do not tell a full story, more can be learned from satellite imagery.
An image captured by Maxar of the site in Sergeyevka shows the sudden appearance of trenches on the grounds of the base in early October.
Later in the month, equipment can be seen assembled in an area in the south of the site, showing it has remained in use. This coincides with the reported arrival of troops in the area and the appearance of the videos, and fits with reports that the North Koreans are training in the area.
Available satellite imagery appears to show that a nearby training site in Lifarevka is also currently in use.
A comparison of low and high-resolution imagery captured over the month of October shows several huts appear to have been renovated at the site.
Training trenches and signs of activity can be seen in high-resolution images captured on 24 October.
Fighting in the Ukrainian frontlines often involves the use of trenches resembling those seen at both sites.
A North Korean flag appears on the frontline
Amid reports of North Korean troops being prepared for fighting in Ukraine, an image showing the North Korean flag next to that of Russia went viral.
Sky News has geolocated this to a former mining facility between the towns of Hirnyk and Tsukuryn in eastern Ukraine.
The site sits close to the frontline, with Tsukuryn being captured by the Russians in early October.
While the presence of the North Korean flag does not necessarily signal their arrival in Ukraine, it does suggest that frontline Russian forces are aware of North Korea's increasing involvement in the conflict.
Weapon deliveries
North Korean support for the Russian war effort is not a new phenomenon.
In October 2023, the White House released imagery showing a Russian ship collecting containers of what the Americans claim were weapons from the North Korean port of Rason.
Prior to this time, the port at Rason had largely been empty. Sky News found there was little activity at its piers until the late summer, after which an increasing number of ships were visible throughout the autumn and winter.
Between late August and mid-February, Sky News recorded 34 days during which ships were visible at Rason's once-empty piers.
While it is not publicly known how much weaponry has been provided by North Korea, the White House alleged in February that 10,000 containers of ammunition and other military materials had been sent since September 2023.
The Data and Forensics team is a multi-skilled unit dedicated to providing transparent journalism from Sky News. We gather, analyse and visualise data to tell data-driven stories. We combine traditional reporting skills with advanced analysis of satellite images, social media and other open source information. Through multimedia storytelling we aim to better explain the world while also showing how our journalism is done.