As Russian troops were retreating in northeastern Ukraine amid a fierce counteroffensive by Kyiv, Muscovites were celebrating the 875th anniversary of the city's founding. Fireworks boomed and President Vladimir Putin inaugurated a huge Ferris wheel, a new transportation link and sports arena.

The Russian capital's festive holiday weekend stood in stark contrast to the military debacle unfolding in Ukraine that seemed to catch the Kremlin by surprise in the nearly 7-month-old war.

The rapid and reportedly chaotic troop withdrawal in the Kharkiv region, in which some weapons and ammunition were left behind, was a huge blow to Russian prestige. It was its largest military defeat in Ukraine since Moscow pulled back its forces from areas near Kyiv after a botched attempt to capture the capital early in the invasion.

As he attended the holiday celebrations that included the inauguration of the Ferris wheel — bigger than the iconic London Eye and now Europe's largest such amusement ride — Putin said nothing about the key moment in Ukraine.

Indeed, the Ukrainian counteroffensive appears to have left the Kremlin struggling for a response.

The Defense Ministry declared the troop pullback was intended to strengthen Russia's forces in the Donbas, a somewhat weak excuse, given that Russia-held areas in the Kharkiv region provided a key vantage point for Moscow's operations in the Donetsk region to the south.

The ministry hasn't offered any specifics about the pullback, but it released a map Sunday showing the Russian troops that were pressed back along a narrow patch of land on the border with Russia — a tacit admission of big Ukrainian gains.

Russian state television and other government-controlled media followed suit, avoiding a direct mention of the retreat while extolling the performance by Russian forces in individual combat episodes.

A Defense Ministry video showed a Russian helicopter gunship attacking Ukrainian troops trying to cross the Oskil River in a previously quiet part the Kharkiv region, an acknowledgement of the broad scale of the ongoing Ukrainian attack.

Many in Russia blamed Western weapons and fighters for the setbacks. "It's not Ukraine but all of NATO who is fighting us," wrote Alexander Kots, a war correspondent for the pro-Kremlin newspaper Komsomolskaya Pravda.

The new Ukrainian blitz, which has boosted the country's morale as the war passed 200 days on Sunday, could set the stage for further gains in the east and elsewhere.

But it also could potentially trigger an even more violent Moscow response, leading to a new and dangerous escalation of hostilities. On Sunday night, Russian missiles struck key Ukrainian infrastructure targets, knocking out power in several regions.

"The Kremlin seems stunned, and has not yet come up with a plan as to how to try and spin this, so to a large extent the media are ignoring the bad news until they get a directive," said Mark Galeotti, a professor at University College, London, who specializes in Russian security affairs.

He described the situation a "sign that the state's control over the narrative is cracking."

In a stark reflection of internal tensions provoked by Kyiv's successes, the Kremlin-backed regional leader of Chechnya, Ramzan Kadyrov, openly criticized the Russian Defense Ministry for "mistakes" that made Ukrainian gains possible.

The criticism from Kadyrov, who has sent Chechen units to fight in Ukraine and repeatedly pushed for tougher action in bellicose language, has revealed new rifts over the course of action in Ukraine.

On another flank, liberal politician Boris Nadezhdin warned on broadcaster NTV that Russia won't be able to defeat Ukraine, and he called for negotiations.

Nadezhdin's statement, made during a carefully orchestrated talk show, appeared to reflect widening doubts in some quarters of Russian officialdom about the future of the Ukraine operation and could be part of efforts to float possible policy shifts.

The Ukrainian blitz and the Kremlin's failure to mount a quick response has infuriated Russian nationalist commentators and military bloggers, who chastised Defense Ministry brass for failing to foresee and fend off the counteroffensive.

Igor Strelkov, a Russian officer who led Moscow-backed forces in the early months of the separatist conflict in eastern Ukraine after it erupted in 2014, denounced top Russian military officials as "morons" for underestimating Kyiv.

Strelkov pointed out that a sizable Russian force blunted Ukrainian attacks in late August and early September in the country's south. But he said the number of troops in the Kharkiv region was woefully insufficient to handle a counteroffensive.

"It turned out that the enemy is capable of simultaneously mounting large-scale offensives at several fronts, including the one where we only had a thin chain of outposts lined up in one echelon with even tactical reserves missing," Strelkov said.

He warned that Ukraine could launch a new offensive in the Donetsk region south to Mariupol. The city on the Sea of Azov fell in May after nearly three months of fierce battles, giving Russia a long-coveted land corridor from its border to the Crimea Peninsula that Moscow annexed in 2014.

"Having the initiative, high combat spirits and powerful groups of strike forces, the enemy will be unlikely to give our troops time to regroup," Strelkov said, noting Ukraine will try to take advantage of the few remaining weeks of good weather before autumn rains make it harder to maneuver.

Many military bloggers criticized the Kremlin for failing to take stronger action and stubbornly trying to win what Moscow calls a "special military operation" with a limited force smaller than Ukraine's.

Ukraine has conducted a broad mobilization with a goal to reach an active military of 1 million fighters, but Russia has continued to rely on a limited contingent of volunteers, fearing that a mass mobilization could fuel broad discontent and cause political instability.

Russia has not said how many of its troops are involved in the war, but Western estimates at its start put the invading force at up to 200,000. Western observers said the recruitment of new volunteers and the use of private military contractors failed to compensate for the heavy losses.

While Moscow hasn't reported its own losses since March when it said that 1,351 soldiers had been killed in the war's first month, Western estimates put the toll as high as 25,000 dead, with the wounded, captured and deserters bringing overall Russian losses to more than 80,000.

Many pro-Moscow military bloggers also wondered why Russia has failed to destroy Ukrainian power plants, communications facilities and bridges on the Dnieper River that are a conduit for Western weapons, fuel and other supplies to the front line. They say Russian missile strikes on railway facilities and power plants have been sporadic and insufficient for inflicting lasting damage.

The Sunday night missile barrage on Ukrainian power plants seemed to respond to those questions in an apparent signal that Moscow could ramp up strikes on vital infrastructure. Ukrainian authorities said Monday that power was quickly restored to most areas.

Strelkov and other nationalist commentators are urging even stronger blows.

"It was necessary to strike Ukraine's critical infrastructure from Day One of the operation," Strelkov said on his messaging app channel. "Strikes on power plants will be quite useful for winning the war."