Ukrainian servicemen ride an armored fighting vehicle in the Sumy region, near Ukraine’s northeastern border with Russia on Sunday. Ukrainian troops in this area crossed into western Russia last week and have seized a large swath of territory.

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Ukrainian servicemen ride an armored fighting vehicle in the Sumy region, near Ukraine’s northeastern border with Russia on Sunday. Ukrainian troops in this area crossed into western Russia last week and have seized a large swath of territory. / AFP via Getty Images

KYIV, Ukraine — Ukrainian troops and Russian reinforcements appeared to be gearing up for a major confrontation in the villages and towns of western Russia in the wake of a surprising Ukrainian offensive in the region.

The Ukrainian forces surged into Russia's Kursk region, just across the border from Ukraine, catching the Russians by surprise and encountering limited resistance in the first few days of the campaign, which began last Tuesday. The Ukrainian advances slowed over the weekend, though it was not clear whether the Ukrainians were meeting greater resistance or simply wanted to consolidate gains they've already made.

In his nightly video address, Ukrainian President Volodymyr Zelensky said Saturday he was receiving regular updates on the operation that's designed to "push the war into the aggressor's territory."

The president added that the offensive is "exactly the kind of pressure that is needed — pressure on the aggressor."

These were Zelenskyy's most explicit remarks about the offensive, which tight-lipped Ukrainian officials had refused to even acknowledge for the first few days.

Ukrainian soldiers are posting to social from inside Russia

The Ukrainians are still not providing details, though some information is starting to emerge. Ukrainian troops are beginning to post on social media from inside Russia. They show themselves tearing down Russian flags in villages they've captured, or standing in front of road signs to indicate they’ve entered a town.

In Russia, military and other security officials are offering terse statements about Russia's intent to quickly drive back the Ukrainians and reclaim the Russian border. Russian television is showing columns of tanks and armored vehicles heading into the Kursk region.

In this pool photograph distributed by Russian state owned Sputnik agency, Russia's President, Vladimir Putin attends a remote meeting with Kursk Region Governov via video call in Moscow, on Friday. Ukraine's incursion into Russia appears to be an unprecedented assault which experts say could aim to draw Russian resources away from other areas or to undermine morale.

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In this pool photograph distributed by Russian state owned Sputnik agency, Russia's President, Vladimir Putin attends a remote meeting with Kursk Region Governov via video call in Moscow, on Friday. Ukraine's incursion into Russia appears to be an unprecedented assault which experts say could aim to draw Russian resources away from other areas or to undermine morale. / AFP via Getty Images<br>

However, many Russian military bloggers remain largely critical of Russia's response, describing it as slow and disorganized.

Tens of thousands of Russian civilians fled Kursk as Ukraine's military moved in, and some have gone on social media to complain that the Russian government gave them no warning and provided no organized evacuation. Many said they fled their homes on short notice, taking only a few possessions they tossed into a car.

Russian President Vladimir Putin said those displaced from their homes would receive 10,000 rubles, the equivalent of $115 at the current exchange rate.

Another battle for Kursk

The Ukrainian operation is being described as the first time a foreign country has taken control of part of Russia or the Soviet Union since Nazi Germany invaded in World War II. That war featured a monumental battle between the Nazis and the Soviet army in Kursk, which historians describe as the largest tank battle ever, and one of the biggest battles in the war. The Soviets came out on top after more than a month of fighting in July and August 1943, a battle seen as critical in the defeat of the Nazis.

The opposing armies in Kursk today are far smaller, but the Ukrainian offensive has already altered the dynamics of a war.

Russia has been on the offensive for months and has been steadily advancing in the eastern region of Donbas, taking a number of villages. The Russians have suffered heavy casualties with their waves of ground attacks.

Villages have largely been reduced to rubble by the time the Russians claim them, and military analysts say they have no strategic value. Still, the Russian advances reflect an advantage in troops and firepower that Ukraine has struggled to overcome throughout the war.

Ukraine's objectives are not yet clear

The surprise Ukrainian offensive has boosted the spirits of Ukrainians and dealt the Russians an unexpected setback on their own territory. The operation has again demonstrated Ukraine's ability to carry out actions that have caught the Russians flat-footed.

"Ukraine still has both the initiative and the momentum behind this operation," said Michael Kofman, with the Carnegie Endowment for International Peace in Washington. "But it's objectives are not clear. If Ukraine is more successful than anticipated, then they become more ambitious. Alternatively, if the operation does not goes well, then they may become more conservative and downsize their goals."

He stressed that Ukraine is taking a major gamble with the operation since its forces are already stretched thin, particularly on the main battleground in the eastern part of the country.

"If Ukraine is struggling to hold its own prepared defenses on its territory, how is it going to hold up in Kursk, in Russian territory?" said Kofman, who makes periodic visits to the frontlines in Ukraine, most recently in June. "How will Ukraine deal with an expanded amount of territory that it has to defend, on top of the frontline where it is currently being pushed back?"

The Biden administration said Ukraine did not provide advance notice of the incursion into Russia. The U.S. administration, which is wary of action that could lead to an escalation or a wider war, has not expressed opposition to Ukraine's offensive, though it says it wants to know more about Ukraine's intent.

Meanwhile, Russia is not letting up in its bombing campaign against Ukrainian cities, which killed more than 20 Ukrainian civilians in recent days.

Ukraine’s air force said Sunday it shot down all but a few of the 57 drones Russia launched overnight at about a dozen different cities and towns. Russia also fired four large North Korean-made missiles. Ukraine says these missiles were also hit in flight, but the falling debris still makes them dangerous.

Local residents walk past a residential house, heavily damaged following a Russian missile strike on Sunday, in a village in the Brovary district, Kyiv region, amid the Russian invasion of Ukraine. Fragments of a missile fell on residential buildings in Brovary district, near Kyiv, the State Emergency Service of Ukraine said on Telegram.

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Local residents walk past a residential house, heavily damaged following a Russian missile strike on Sunday, in a village in the Brovary district, Kyiv region, amid the Russian invasion of Ukraine. Fragments of a missile fell on residential buildings in Brovary district, near Kyiv, the State Emergency Service of Ukraine said on Telegram. / AFP via Getty Images

A 35-year-old man and his 4-year-old son were killed when remnants of a missile crashed into their apartment building in a suburb of the capital Kyiv, officials said. They were among eight Ukrainian civilians killed in various attacks on Saturday and Sunday.

A Russian missile strike on Friday set off a massive fire at a supermarket in the eastern town of Kostiantynivka, leaving 14 dead and dozens wounded, officials added.