Russian forces launched massive missile strikes on Ukraine’s Kyiv and Chernihiv regions on Thursday, areas that have not 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 and an "infrastructure object" was hit. It was not immediately clear if there were any casualties.

Vyshhgorod is located 20 kilometers (about 12 miles) north of downtown Kyiv. Kuleba linked the strikes with the Day of Statehood, which Ukraine marked for the first time on Thursday.

"Russia, with the help of missiles, is mounting revenge for the widespread popular resistance, which the Ukrainians were able to organize precisely because of their statehood," Kuleba told Ukrainian television. "Ukraine has already broken Russia’s plans and will continue to defend itself."

Chernihiv governor Vyacheslav Chaus reported that multiple missiles were fired from the territory of Belarus at the village of Honcharivska.

Russian troops withdrew from the Kyiv and Chernihiv regions months ago after 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, Odessa, Dnipropetrovsk, Kharkiv, Zaporizhzhia, Lutsk."

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

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

Ukraine has made clear it intends to recapture Kherson, which fell to Russia in the early days of the invasion launched by Russian President Vladimir Putin on Feb. 24.

Britain's Defense Ministry said Ukrainian forces have probably established a bridgehead south of the Inhulets River, and had used new, long-range artillery to damage at least three of the bridges crossing the Dnipro.

"Russia's 49th Army, stationed on the west bank of the Dnipro River, now looks highly vulnerable," it said in a regular intelligence bulletin on Twitter, adding that Kherson was virtually cut off from the other territories occupied by Russia.

"Its loss would severely undermine Russia's attempts to paint the occupation as a success."

The British military estimated 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 ministry said.

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.

Oleksiy Danilov, secretary of Ukraine's National Security and Defense Council, earlier tweeted that Russia was concentrating "the maximum number of troops" in the direction of the Kherson but gave no details.

Oleksiy Arestovych, an adviser to Ukrainian President Volodymyr Zelenskyy, said Russia was conducting a "massive redeployment" of forces from the east to the south in what amounted to a strategic shift from attack to defense.

Zelenskyy said Ukraine would rebuild the Antonivskyi Bridge over the Dnipro and other crossings in the region.

"We are doing everything to ensure that the occupying forces do not have any logistical opportunities in our country," he said in a Wednesday evening address.

Ukraine’s presidential office said Thursday morning that Russian shelling of cities and villages over the past 24 hours killed at least five civilians, all of them in the eastern Donetsk region, and wounded nine more.

Russian officials had earlier said they would turn instead to pontoon bridges and ferries to get forces across the river.

Russian-backed forces on Wednesday said they had captured the Soviet-era coal-fired Vuhlehirsk power plant, Ukraine's second-largest, in what was Moscow's first significant gain in more than three weeks.

Diplomacy

Meanwhile, U.S. Secretary of State Antony Blinken said he planned a phone conversation with Russian Foreign Minister Sergei Lavrov - the first between the two diplomats since the start of the war.

The call in the coming days would not be "a negotiation about Ukraine," Blinken said at a news conference, restating Washington's position that any talks on ending the war must be between Kyiv and Moscow.

Russia has received no formal request from Washington about a phone call between Blinken and Lavrov, TASS news agency reported.

The United States has made "a substantial offer" to Russia for it to release U.S. citizens WNBA star Brittney Griner and former U.S. Marine Paul Whelan, Blinken said, without giving details of what the United States was offering in return.

Blinken said he would press Lavrov to respond to the offer.

A source familiar with the situation confirmed a CNN report that Washington was willing to exchange Russian arms trafficker Viktor Bout, who is serving a 25-year prison sentence in the United States, as part of a deal.

Aside from discussing Americans detained by Russia, Blinken said he would raise with Lavrov the tentative deal on grain exports reached last week between Russia, the United States, Turkey and Ukraine.

Russia reduced gas flows to Europe on Wednesday in an energy stand-off with the European Union. It has blocked grain exports from Ukraine since invading but on Friday agreed to allow deliveries through the Black Sea to Turkey's Bosporus Strait and on to global markets.

The deal was almost immediately thrown into doubt when Russia fired cruise missiles at Odessa, Ukraine's largest port, on Saturday, just 12 hours after the deal was signed.

Before the invasion and subsequent sanctions, Russia and Ukraine accounted for nearly a third of global wheat exports.