Ukrainian troops staged a surprise cross-border attack into Russia early last week, and now Kyiv claims to control more than 1,100 square kilometres of its neighbour's territory.
The incursion has reframed the war and caused chaos in western Russia's Kursk region.
It is the largest foreign attack on sovereign Russian territory since World War II.
More than 120,000 civilians have been evacuated, according to Russian authorities.
And Kyiv says it has captured at least 82 settlements.
This is how the incursion is tracking after nearly 10 days of fighting in the region.
Ukraine pushes into Kursk
On August 6, thousands of Ukrainian troops surged across the border from Ukraine's north-eastern Sumy region.
The attack took place in the town of Sudzha in Russia's Kursk region, located 530km from Moscow.
Early on, Russia's defence ministry said its forces had engaged Ukrainian troops near the villages of Tolpino and Obshchy Kolodez, about 25km and 30km from the Russia-Ukraine border.
In comparison, the Russian advance into Kharkiv this year penetrated about 8km into Ukraine.
Ukrainian President Volodymyr Zelenskyy said on Thursday, local time, his country's troops had taken full control of Sudzha.
Russia didn't immediately respond to his claims.
Although it had a pre-war population of only about 5,000 people, Sudzha is the Kursk region's administrative centre.
It is larger than any other towns or settlements Ukraine has taken since the incursion began.
Sudzha also has the only pumping station that delivers Russian natural gas to Europe through Ukraine.
It accounts for about 3 per cent of Europe's imports. There has been no indication of any disruption to the gas flow.
Regions declare state of emergency
After a week, Ukraine's top commander claimed to control 1,150 sq km of Russian territory.
Although analysts have suggested the true scale was smaller.
The Institute for the Study of War (ISW), a US-based think tank that tracks developments on the frontline, has estimated about 800 sq km.
It said Ukraine had captured more land in a week than Russian forces had taken in Ukraine in seven months.
The regions of Kursk and neighbouring Belgorod have both declared a state of emergency.
The Kursk region has a population of about 1.2 million, and so far more than 120,000 civilians have been forced to flee, according to Russian authorities.
Belgorod is a region of forests, farmland and rolling hills and has a 540km border along Ukraine's north-eastern edge.
It has a population of about 1.5 million.
It holds about 40 per cent of Russia's iron ore and other minerals, and is home to several major industrial companies and farms.
Russian Defence Minister Andrei Belousov said the general staff had prepared a series of measures to defend Russia's border regions of Kursk, Bryansk and Belgorod — which cover an area about 30 sq km larger than Tasmania.
Settlements captured
Earlier this week, the acting governor of Kursk region, Alexei Smirnov, said 28 communities had fallen to Ukrainian forces.
Ukraine's top commander Colonel General Oleksandr Syrskyi told Mr Zelenskyy on Thursday that the incursion had so far advanced 35km into the Kursk region, capturing 82 settlements.
Russian military bloggers claimed that Ukrainian forces had advanced into the city of Krasnooktyabrskoye, which is 1km from the international border, according to ISW analysis on August 14.
Geolocated footage published on August 13 showed Ukrainian forces operating in eastern Zhuravli, indicating that Ukrainian forces advanced in the eastern part of the settlement.
Kyiv also claims to have captured hundreds of Russian prisoners of war.
Ukrainian special forces said a group of more than 100 Russian soldiers were taken in a single operation.
Images have shown blindfolded men, who appear to be Russian soldiers, being escorted through the Ukrainian Sumy region in the back of a military truck.
Ukraine's human rights commissioner Dmytro Lubinets said this week that he had talks with his Russian counterpart about a prisoner exchange.
Satellite images show airfield attacks
Ukraine has reportedly attacked several airfields in Russia.
A satellite photo from Planet Labs PBC shows the Borisoglebsk Air Base in Russia after an attack by Ukrainian drones on August 14.
Separately, at Savasleika Air Base, one burn mark could be seen just off the runway in images on Wednesday.
Mr Zelenskyy thanked Ukraine's Security Service (SBU) and military for conducting drone strikes against unspecified Russian air bases.
Satellite imagery collected by Maxar from the last two days shows a trench dug across the countryside near the city of Lgov in Russia's Kursk region.
Lgov is about 40km from what is thought to be the deepest penetration of Ukrainian troops.
The Russian trench appears to have been dug close to a main highway and rail line.
No ease on eastern frontline
Russia has seen previous raids of its territory in the war, but the Kursk incursion is notable for its size, speed, and the length of time that Ukraine has stayed inside Russia.
Ukraine sent in some of its most battle-hardened Ukrainian brigades.
As many as 10,000 Ukrainian troops are involved, according to Western military analysts.
Mr Zelenskyy spoke cryptically of the need to move on to the "next steps" in public remarks this week, and hinted at other possible offensive actions in Russian territory.
Military analysts believe the main purpose of the incursion is to draw large numbers of Russian troops away from the frontline in the eastern Donetsk region.
Russian forces, which have a vast numerical supremacy and control 18 per cent of Ukrainian territory, have been advancing this year along the 1,000km front.
Ukraine said there was no sign that Russian military pressure was receding along the eastern front inside its borders and reported the heaviest fighting in weeks near the city of Pokrovsk, an important logistics hub.
The head of the Pokrovsk military administration appealed to locals to evacuate, saying Russian forces were getting closer.
If Russian troops capture Pokrovsk, where they've been trying to breach Ukrainian defences for weeks, they would further advance toward their goal of capturing Ukraine's entire Donetsk region.
ABC/Wires
