Russian forces on Thursday launched missile strikes on Ukraine’s Kyiv and Chernihiv regions, areas that haven’t been targeted in weeks, while Ukrainian officials announced an operation to liberate an occupied region in the country’s south.

Kyiv’s regional governor, Oleksiy Kuleba, said on Telegram that a settlement in the Vyshgorod district of the region was targeted early on Thursday morning. An “infrastructure object” was hit; it wasn’t immediately clear if there were any casualties.

The Chernihiv governor, Vyacheslav Chaus, at the same time reported that multiple missiles were fired from Belarus at the Honcharivska community. On Telegram, Ukraine’s northern operational command said that nine missiles fell in the forest close to the community, with no word on casualties. 

Russia’s use of Belarus, which shares borders with Russia and Ukraine as well as NATO-member Poland, as a launchpad for attacks on Ukraine has long been a source of concern for Kyiv. The Belarusian leader, Alexander Lukashenko, operates in lockstep with President Putin and reportedly wants his forces to play a more active role in Russia’s war against Ukraine. Some of that may be bluster, but as today’s missile attack — characterized by Ukrinform as “massive” — demonstrates, the situation could escalate.

Russian troops withdrew from the Kyiv and Chernihiv regions months ago, failing to capture either. The renewed strikes on the areas come a day after the leader of pro-Kremlin separatists in the east, Denis Pushilin, publicly called on the Russian forces to “liberate Russian cities founded by the Russian people — Kyiv, Chernihiv, Poltava, Odesa, Dnipropetrovsk, Kharkiv, Zaporizhzhia, Lutsk.”

Ukraine’s second-largest city, Kharkiv, also came under a barrage of shelling overnight, its mayor, Ihor Terekhov, said. The southern city of Mykolaiv was fired at as well, with one person sustaining injuries.

Meanwhile, the Ukrainian military continued to counterattack in the occupied southern region of Kherson, striking a key bridge over the Dnieper River on Wednesday.

Ukrainian media on Thursday quoted Ukraine’s presidential adviser, Oleksiy Arestovich, as saying that the operation to liberate Kherson “has already begun.” Mr. Arestovich said Kyiv’s forces were planning to isolate Russian troops there and leave them with three options — to “retreat, if possible, surrender, or be destroyed.”

The secretary of Ukraine’s National Security and Defense Council, Oleksiy Danilov, in televised remarks on Wednesday, said he was “cautious” in assessing the timeline of the possible counteroffensive. “I would really like it to be much faster,” he said, adding that “the enemy is now concentrating the maximum number [of forces] precisely in the Kherson direction.”

“A very large-scale movement of their troops has begun, they are gathering additional forces,” Mr. Danilov warned.

The British military estimated Thursday that Ukraine’s counteroffensive in Kherson is “gathering momentum.”

“Their forces have highly likely established a bridgehead south of the Ingulets River, which forms the northern boundary of Russian-occupied Kherson,” the British Defense Ministry said on Thursday.

It added that Ukraine has used its new long-range artillery to damage at least three of the bridges across the Dnieper River, “which Russia relies upon to supply the areas under its control.” The 1,000-meter-long Antonivsky bridge, which Ukrainian forces struck on Wednesday, is likely to be “unusable,” the British Defense Ministry concluded.

Against the backdrop of what amounts to the countdown to a pitched battle for control of Kherson, social media invective was flying from some high quarters. “Today Ukraine celebrates the days of statehood and baptism of Kyivan Rus,” tweeted a top advisor to President Zelensky, Mykhailo Podolyak, adding: “Also today, two dozen missiles were fired at our cities…. Russians can steal refrigerators, but not our history. When Kyiv was a cultural capital, Moscow was a swamp. As it still remains now.”