This photo taken from video released by Russian Defense Ministry Press Service on Monday shows a Russian self-propelled gun firing towards Ukrainian positions at an undisclosed location. Russian Defense Ministry Press Service via Associated Press

KYIV, Ukraine — Ukrainian forces were making a major effort to end months of a battlefield stalemate and punch through Russian defensive lines in southeast Ukraine for a second day, with Russian officials saying on Monday that Moscow’s forces have foiled at least one assault.

Kyiv authorities said their forces were indeed increasing offensive operations and making gains, but suggested some of the Russian announcements were misinformation as speculation grows about a widely anticipated counteroffensive after more than 15 months of war.

Vladimir Rogov, an official in the Russia-backed administration of Ukraine’s partly occupied Zaporizhzhia province, said fighting resumed on its border with the eastern Donetsk province on Monday after Russian defenses beat back a Ukrainian advance the previous day.

“The enemy threw an even bigger force into the attack than yesterday (Sunday),” and the new attempt to break through the front line was “more large-scale and organized,” Rogov said, adding: “A battle is underway.”

Rogov interpreted the Ukrainian military movements as part of an effort to reach the Sea of Azov coast and sever the land corridor to the Crimean Peninsula, which Moscow annexed in 2014. Analysts have long viewed that strategy as likely because it would cut the Russian forces in two and severely strain supplies to Crimea, which has served as a key Russian military hub in the war that started Feb. 24, 2022.

Rogov’s comments came after Moscow also said that its forces thwarted large Ukrainian attacks in Donetsk province, near its border with the Zaporizhzhia province.

Reacting to Russia’s declarations that it repelled Ukrainian offensives, a U.S. official said on the condition of anonymity to discuss sensitive matters that “We have no reason to believe any Russian action has had any spoiling effect on pending or ongoing Ukraine operations.”

Ukrainian Deputy Defense Minister Hanna Malyar said the Ukrainian military has scored gains.

“Despite fierce resistance and attempts of the enemy to hold the occupied lines and positions, our units moved forward in several directions during the fighting,” she said.

Malyar drew no distinctions between phases of the war, insisting that Ukraine’s defense against Russia’s invasion “contains everything, including counter-offensive actions.” She acknowledged that Kyiv’s forces “in some areas … are shifting to offensive operations.”

Retired British Gen. Richard Barrons, co-chair of the U.K.-based strategic consulting firm Universal Defence & Security Solutions, said Ukraine was “clearly in the preliminary phase” of its counteroffensive.

“The focus will be on the tanks and artillery, and infantry — that’s the most visible tip of the spear,” he told The Associated Press, noting that the counteroffensive will also include politics, diplomacy, information and cyber warfare.

Ukraine often waits until the completion of its military operations to confirm its actions.

In this image made from video provided by Ukrainian Defense Ministry on Sunday, a Ukrainian soldier poses for the camera with his fingers to his lips, in an undisclosed location in Ukraine. Ukrainian Defense Ministry via Associated Press

A Ukrainian Defense Ministry video showed soldiers putting a finger to their lips in a sign to keep quiet. “Plans love silence,” it said on the screen. “There will be no announcement of the start.”

Zaporizhzhia and Donetsk are two of the four provinces that President Vladimir Putin claimed as Russian territory last fall and which Moscow partially controls.

Russia’s Defense Ministry said it had pushed back a “large-scale” assault Sunday at five places in Donetsk province. The announcement couldn’t be independently verified, and while Ukrainian officials reported fighting in that area, they didn’t confirm a retreat.

Russian Defense Ministry spokesman Igor Konashenkov said in an unusual overnight video that 250 Ukrainian personnel were killed in the fighting in Donetsk province, and 16 Ukrainian tanks, three infantry fighting vehicles and 21 armored combat vehicles were destroyed.

“The enemy’s goal was to break through our defenses in the most vulnerable, in its opinion, sector of the front,” Konashenkov said. “The enemy did not achieve its tasks. It had no success.”

The Russian ministry said the alleged attack started Sunday morning but it waited until early Monday to announce it.

In response, the Center for Strategic Communications of the Armed Forces of Ukraine said Russian forces were “stepping up their information and psychological operations.”

“To demoralize Ukrainians and mislead the community (including their own population), Russian propagandists will spread false information about the counteroffensive, its directions and the losses of the Ukrainian army. Even if there is no counteroffensive,” a statement on Telegram read.

Ukrainian officials have said for months that a spring campaign with advanced weapons supplied by Western allies to reclaim territory seized by Russia during the war was planned, but they have kept quiet about when, how and where it might start, or whether it had already been launched.

Recent military activity, including drone attacks on Moscow, cross-border raids into Russia and sabotage and drone attacks on infrastructure behind Russian lines, has unnerved Russians. Analysts say those actions may represent the start of the counteroffensive.

This photo taken from video released by Russian Defense Ministry Press Service on Monday shows a Ukrainian military vehicle being hit during combat in Ukraine. Russian Defense Ministry Press Service via Associated Press

In other disruption, TV and radio broadcasts in several regions of Russia were hacked Monday, according to Kremlin spokesman Dmitry Peskov. A fake broadcast featured a voice impersonating Putin and stated that Ukrainian forces had invaded the Belgorod, Bryansk and Kursk regions of Russia.

Those Russian regions have occasionally been targeted in cross-border strikes during the war.

The impersonator announced that martial law was declared in those regions, where people were urged to evacuate, and all Russians eligible for military duty were being mobilized, Peskov said in remarks carried by Russian news agencies.

The Russian military said Monday it repelled the latest Ukrainian incursion into the Belgorod region, on the border in Ukraine. Russians who purport to be fighting alongside Ukrainian forces said they attacked on Sunday. They were driven back by airstrikes and artillery fire, according to the Russian Defense Ministry.

At least two factors have been at play in the counteroffensive’s timing: better ground conditions for the movement of troops and equipment after the winter, and the deployment of more advanced Western weapons and training of Ukrainian troops to use them.

Ukraine’s Western allies have sent the country more than $70 billion in military aid to help its defense. Driving out the Kremlin’s forces is a daunting challenge for Kyiv’s planners. Russia has built extensive defensive lines, including trenches, minefields and anti-tank obstacles.

After months of a battlefield stalemate, with neither side making significant gains and suffering losses of personnel and weapons, Ukraine could launch simultaneous pushes in different areas of the front line that stretches for around 1,100 kilometers (nearly 700 miles), analysts say.

The Russian Defense Ministry spokesman said Ukraine used six mechanized and two tank battalions in the Donetsk attacks. The ministry released a video that it said showed the destruction of some of the equipment in a field.

In the devastated eastern city of Bakhmut, the site of the war’s longest and bloodiest battle, Ukrainian forces reportedly had reclaimed ground. Malyar, the deputy defense minister, said Ukrainian forces are advancing and “occupy dominating heights” around Bakhmut.

The leader of Russia’s Wagner mercenary group, Yevgeny Prigozhin — a frequent critic of his country’s military brass whose statements are sometimes unreliable — said that Russian forces lost control of part of the village of Berkhovka outside Bakhmut. Prizoghin said last month that his forces had seized all of the city of Bakhmut, with Ukrainian forces remaining in control of many surrounding areas.