Ukrainian President Volodymyr Zelenskyy said Thursday that his country's troops had taken full control of Sudzha, the largest Russian town to fall to Ukraine's forces since the start of their cross-border incursion more than a week ago.

Although it had a prewar population of only around 5,000 people, Sudzha is the administrative center for the border area of Russia's Kursk region and is larger than any of the other towns or settlements that Ukraine says it has taken since the incursion began on Aug. 6.

Zelenskyy said Ukraine was setting up a military command office in Sudzha, which suggests that Ukraine might plan to remain in the Kursk region long-term — or just signal Moscow that it may intend to do so. He didn't elaborate on what functions the office might handle, though he said earlier this week that Ukraine would be distributing humanitarian aid to Sudzha residents.

Russia didn't immediately respond to Zelenskyy's claims, but its defense ministry said earlier Thursday that Russian forces had blocked Ukrainian attempts to take several other communities.

The surprise Ukrainian incursion has reframed the war and caused chaos in the Kursk region, leading to the evacuation of more than 120,000 civilians, according to Russian authorities, and the capture of at least 100 Russian troops, according to Kyiv.

Zelenskyy has said one of the reasons for the incursion was to protect neighboring Ukrainian regions. “The more Russian military presence is destroyed in the border regions, the closer peace and real security will be for our state. The Russian state must be responsible for what it has done,” he said Tuesday.

Russia has seen previous raids of its territory in the war, but the Kursk incursion is notable for its size, speed, the reported involvement of battle-hardened Ukrainian brigades, and the length of time they have stayed inside Russia. As many as 10,000 Ukrainian troops are involved, according to Western military analysts.

The incursion also marks the first time foreign troops have invaded and held Russian territory since Nazi Germany did in World War II.

Although Russian military bloggers reported that Russian reserves sent to the Kursk region had slowed Ukrainian advances, questions remain over whether the incursion might force Moscow to move troops to Kursk from front-line positions in eastern Ukraine, where they've made slow but steady advances this year.

As Kyiv was trumpeting its gains in Kursk on Thursday, officials in the eastern Ukrainian city of Pokrovsk, which had a prewar population of about 60,000, warned civilians to evacuate ahead of rapidly approaching Russian troops, who were about 10 kilometers (6 miles) from the city's outskirts. If Russian troops capture Pokrovsk, where they’ve been trying to breach Ukrainian defenses for weeks, they would further advance toward their goal of capturing Ukraine's entire Donetsk region.

White House national security spokesman John Kirby said Thursday that Russia had withdrawn some forces, including infantry units, from Ukraine and was shifting them to Kursk, but that the U.S. didn't know how many troops were involved.

However, a U.S. official, speaking on condition of anonymity because of not being authorized to comment publicly, said it doesn't appear that Russia has moved a sufficient number of armored battalions or other types of combat power from the front line in Ukraine to Kursk, and that Moscow will need to shift more troops to repel Kyiv's forces.

Asked Thursday if the Pentagon was considering limiting any support to Ukraine in light of the latest incursion, spokeswoman Sabrina Singh said it doesn’t affect what the U.S. is sending, but that, “you’ve seen us modify and give different capabilities over time, and we reserve that right to continue to do that.”

Russian military bloggers reported that small Ukrainian mechanized groups have continued to probe Russian defenses. And satellite images analyzed by The Associated Press on Thursday show that a Ukrainian drone attack on Russian air bases damaged at least two hangars and other areas.

Images taken Wednesday by Planet Labs PBC show that two hangars at Borisoglebsk Air Base have been struck, with a field of debris around both. It was not immediately clear what purpose the hangars served. There also appeared to be potential damage to two fighter aircraft at the base.

Separately, at Savasleika Air Base, one burn mark could be seen just off the runway in images Wednesday, though there was no apparent damage to the fighter jets and other aircraft there.

As of Thursday, the Ukrainian military claimed to be holding more than 80 towns and settlements in the Kursk region.

Kursk's acting governor, Alexei Smirnov, on Thursday ordered the evacuation of the Glushkovo region, about 45 kilometers (28 miles) northwest of Sudzha. The order suggests Ukrainian forces were gradually advancing toward the area.

At a facility receiving evacuees, Tatyana Anikeyeva told Russian state television about her ordeal fleeing from the fighting. “We were rushing from Sudzha. … We hid in the bushes. Volunteers were handing out water, food, bread to people on the go. The sound of the cannonade continued without any break. The house was shaking."

Evacuees milled around and waited in long lines for food and other supplies. One man stroked his pet dog and tried to comfort her, while saying that he felt nauseous and had no appetite.

Russia also declared a federal-level state of emergency in the Belgorod region, a day after a regional-level declaration was made for the area. The change in status suggests that officials believe the situation is worsening and hampering the region’s ability to deliver aid.

Ukraine’s chief military officer, Gen. Oleksandr Syrskyi, said earlier this week that Ukrainian forces had taken 1,000 square kilometers (about 390 square miles) of the Kursk region, though his claim couldn't be independently verified. The contact lines in Kursk have remained fluid, allowing both sides to maneuver easily, unlike the static front line in eastern Ukraine, where it has taken Russian forces months to achieve even incremental gains.

Russian officials have pushed back on Syrskyi's territorial claim. Speaking to reporters Wednesday at the U.N., Russia's deputy ambassador, Dmitry Polyansky, called the incursion an “absolutely reckless and mad operation,” and said Ukraine's aim to force Russia to move its troops from eastern Ukraine is not happening because “we have enough troops there.”

Sudzha has a measuring station for Russian natural gas that flows through Ukrainian pipelines and a ccounts for about 3% of Europe’s imports. There has been no indication of any disruption to the gas flow.