Russia is preparing to step up its attacks on Ukraine using Iranian-made exploding drones, according to President Zelensky, as Moscow looks for ways to keep up the pressure on Kyiv after months of battlefield setbacks for the Kremlin’s war strategy.

“We have information that Russia is planning a prolonged attack by Shaheds,” Mr.  Zelensky said in his nightly video address late Monday, referring to the exploding drones.

He said the goal is to break Ukraine’s resistance by “exhausting our people, [our] air defense, our energy,” more than 10 months after Russia invaded its neighbor.

President Putin is exploring how to shore up confidence in Moscow’s flawed war effort, which in recent months has been dented by a Ukrainian counteroffensive backed by Western-supplied weapons. That has brought criticism in some Russian circles of the military’s performance.

In the latest embarrassment for the Kremlin, Ukrainian forces fired rockets at a facility at Makiivka, a city of about 300,000 people 10 miles east of Donetsk, where Russian soldiers were stationed, killing 63 of them on New Year’s Eve. It was one of the deadliest attacks on the Kremlin’s forces since the war began more than 10 months ago.

Ukraine’s claims to have taken out 400 soldiers in the attack could not be independently verified, but the official description of the incident did little to remove the long shadow of internecine conflict in the region: “Santa packed close to 400 corpses of pigdogs in his sack,” the strategic communications branch of Ukraine’s armed forces wrote in a Telegram post.  

The deputy speaker of the Moscow City parliament, Andrey Medvedev, has called for retribution for the slain soldiers. He was joined by a Russian lawmaker, Grigory Karasin, who called for “an exacting internal analysis” and vengeance against both Kyiv and NATO. 

Ukraine’s Western-reinforced air defenses have made it difficult for Russian warplanes to carry out missile strikes. The Iranian-made exploding drones are a relatively inexpensive weapon that also spreads fear among troops and civilians. America and its allies have sparred with Iran over Tehran’s role in allegedly supplying Moscow with the drones.

The Institute for the Study of War said that Mr. Putin is looking to strengthen support for his strategy among key voices in Russia.

“Russia’s air and missile campaign against Ukraine is likely not generating the Kremlin’s desired information effects among Russia’s nationalists,” the think tank said late Monday.

“Such profound military failures will continue to complicate Putin’s efforts to appease the Russian pro-war community and retain the dominant narrative in the domestic information space,” it added.

Mr. Zelensky warned that in the coming weeks, “the nights may be quite restless.” He added that during the first two days of the new year, which were marked by relentless nighttime drone attacks on Ukrainian cities and energy infrastructure, the country’s forces shot down more than 80 Iranian-made drones.

As well as hoping to wear down resistance to Russia’s invasion, the long-range bombardments have targeted the power grid to leave civilians at the mercy of biting winter weather as power outages ripple across the country.

“Every downed drone, every downed missile, every day with electricity for our people and minimal shutdown schedules are exactly such victories,” Mr. Zelensky said.

In the latest fighting, a Russian missile strike overnight on the city of Druzhkivka in the partially occupied eastern Donetsk region wounded two people, the deputy head of Ukraine’s presidential office, Kyrylo Tymoshenko, reported Tuesday.

Officials said the attack ruined an ice hockey arena described as the largest hockey and figure skating school in Ukraine.

Overnight Russian shelling was also reported in the northeastern Kharkiv region and the southeastern Dnipropetrovsk region.

In the recently retaken areas of the southern Kherson region, Russian shelling on Monday killed two people and wounded nine others, Kherson’s Ukrainian governor, Yaroslav Yanushevich, said Tuesday. He said the Russian forces fired at the city of Kherson 32 times on Monday.

In the meantime, Ukrainian strikes inside Russia, including several at military airbases, are likely to continue. The head of Ukrainian intelligence, Kyrylo Budanov, told Australia’s ABC that such attacks will go “deeper and deeper” inside Russia. Mr. Budanov intimated that the Russian-occupied Crimean peninsula will also come under attack: “Crimea — it’s a part of Ukraine. It’s our territory. We can use any weapon on our territory,” Mr. Budanov told the Australian network.