Zelensky claims to occupy the Russian city
Foreign troops have entered Russian territory for the first time since World War II.
Ukrainian President Volodymyr Zelensky has claimed that the Ukrainian army has captured a Russian city.
Zelensky said Thursday that his forces had taken control of the Russian town of Sudza less than a week after crossing the border into Russia's Kursk region.
BBC, CNN and other media reported that Kiev forces have been stationed in the Russian city 105 kilometers (65 miles) southwest of the city of Kursk since last Wednesday.
Although nothing has been said by Russia so far, the president of Ukraine was the first to confirm that his forces have taken over the city.
Ukrainian army chief Oleksandr Sirsky said his troops had advanced 35 kilometers (21.7 miles) into Russian resistance and captured 1,150 square kilometers of territory and 82 settlements after launching a surprise attack.
Sirski said a military office has been set up in the occupied city of Sudja to maintain law and order and meet the priority needs of the people.
Sudza city is located near one of the most important gas terminals in Russia. Sudza is the main gas supply route through Ukraine to Europe. It is believed that one of the goals of Kiev's forces to occupy the city may be to cut off a profitable source of income for Moscow.
Tens of thousands of Russians have fled their homes in the face of an onslaught in Ukraine, and Russia's military has been left behind as it stumbles against Kiev's forces.
Earlier on Wednesday, Ukrainian drones carried out the largest attack targeting four Russian air bases. A Ukrainian security source told CNN that the attack targeted four bases in Kursk and Voronezh in the southwest and the Nizhny Novgorod region east of Moscow.
However, Russia's Defense Ministry claimed it had destroyed 117 'aircraft-like' drones and four strategic missiles in Kursk and surrounding areas.
While the Ukraine attack has created a major embarrassment for the Kremlin on the one hand, it is also clear that Kiev has made significant changes in its strategy.
Because, this is the first time after the Second World War that foreign troops entered the territory of Russia.
A Ukrainian military commander told CNN on Wednesday that Russian reserve forces have withdrawn from key battlegrounds in Ukraine and occupied Crimea to stop Kiev's advance.