Inside Ukraine's new northern frontline
While fighting continues in the east, a new front has been opened in the north of Ukraine.
In the early hours of Friday 10 May, Russian ground troops, backed by warplanes, drones and artillery, crossed the Ukrainian border into Kharkiv region.
In recent months, fighting in Ukraine has been focused across front lines in the east of the country. This development has focused attention on Ukraine's northeast and its second city of Kharkiv, which lies less than 20 miles from the border.
Fighting around Vovchansk
Footage captured in the early stages of the Russian offensive shows a group of Ukrainian soldiers fighting in woodland.
Sky News has geolocated a section of this clip, which shows the troops withdrawing south, away from the border.
Other video provided to Sky News by Ukrainian sources sheds further light on how fighting unfolded in the early stages of Russia's assault from the north.
Filmed from a drone, footage shows a group of Russian soldiers on Tuesday entering Vovchansk along the main road connecting to the town from the northwest.
In separate footage, a group can be seen moving southwest around 140 metres from this position. A further 400 metres in this direction, a group was filmed being targeted by Ukrainian forces while appearing to carry one of their wounded.
Other videos shared by the Ukrainians show that by this time, some Russian forces had moved from the outskirts into a residential area in the west of Vovchansk. They can be seen moving between buildings and are filmed being targeted by a Ukrainian drone.
Footage posted on 16 May suggests Russian troops in the area have been able to make steady progress through the town from the northwest. A group was filmed outside the town's hospital, with one falling from the building's first floor.
While on the ground, fighting in Vovchansk appears to have been relatively contained to the west of the town, it has been subject to intense bombing in recent days.
Drone footage posted on 14 May captured smoke rising from multiple locations across the town, showing the scale of Russian shelling.
Just west of Vovchansk, Russian forces entered the villages Buhruvatka and Ohirtseve.
In a photograph geolocated to Ohirtseve by Sky News, a group of soldiers posed with a flag bearing the face of Chechnya's former leader Akhmad Kadyrov, who was killed in 2004.
Russians advance towards Lyptsi
Further west, Russian forces have made progress in the direction of the town of Lyptsi. Located just south of the Russian border, the town is a mere 20km from the city of Kharkiv.
Geolocated images suggest some Russian forces approached the Ukrainian border from multiple locations. One posted on 10 May shows a collection of destroyed Russian vehicles just north of the Ukrainian border town Pylna.
Footage released on 11 May suggests this was not the only point at which Russians attempted to cross the border, as the video shows a Ukrainian drone targeting Russian vehicles between the towns of Strilecha and Krasne.
From the north, Russian troops moved towards Lyptsi along a road running southwest from the border. Videos posted in recent days show they were targeted repeatedly by Ukrainian drones along this route.
Drone footage posted on 15 May shows the scale of shelling that accompanied this ground offensive, targeting Ukrainian positions ahead of Russian forces.
While Russia has made significant progress in their push south, Ukrainian forces have fought back. Footage posted on 15 May shows a Russian position just north of Lyptsi being bombed and approached by a group of Ukrainian soldiers, who are filmed capturing surviving Russians.
A 'buffer zone'
While it is yet to be seen how far Russian troops will advance from the north, Vladimir Putin has claimed that the offensive is not an effort to capture the city of Kharkiv.
In a statement on 17 May, he said: "I have said publicly that if it continues, we will be forced to create a security zone, a sanitary zone," claiming this was the current goal of Russian troops in the north of Ukraine.
For the moment, most fighting is still concentrated in the east, where Russia occupies vast areas of Ukrainian territory.
