Russian shelling in eastern Ukraine's Kharkiv Oblast over the past 24 hours left four civilians dead, the regional governor said Wednesday.

A woman was killed in the village of Zolochev, while a 12-year-old boy died in the village of Ivanivka, northwest of Kharkiv city. Two more people were killed in the village of Shestakove, northeast of Kharkiv city. Seven other civilians were injured in the region, according to Kharkiv Oblast Gov. Oleg Synegubov.

"The enemy is acting insidiously, striking at civilians and civilian infrastructure," Synegubov said in a statement via Telegram. "But he will answer for all his crimes! Ukraine will win!"

Over half of Sieverodonetsk is now likely occupied by Russian forces, including Chechen fighters, the U.K. Ministry of Defense said Wednesday in an intelligence update.

The ministry said fighting intensified in the streets of the key eastern Ukrainian city on Monday and Tuesday, "with Russian forces pushing closer to the town centre." Sieverodonetsk is located in the war-torn Luhansk Oblast of eastern Ukraine's disputed Donbas region.

"Russian ground operations remain tightly focused, with the weight of fire power concentrated within a small sector of Luhansk Oblast," the ministry said.

"Beyond the Donbas, Russia continues to conduct long-range missile strikes against infrastructure across Ukraine," the ministry added. "The strategically important bridge links Ukraine with Romania and with Ukraine's ports on the Danube, which have become critical to Ukrainian exports after the blockade of Ukrainian Black Sea ports by Russia."

The U.S. will provide Ukraine with "more advanced rocket systems and munitions," President Joe Biden confirmed in a New York Times op-ed published Tuesday.

The systems "will enable them to more precisely strike key targets on the battlefield in Ukraine," he wrote.

Russian Foreign Minister Sergei Lavrov warned last week that providing more advanced rockets would be a new "unacceptable escalation" because they could hypothetically be used to strike within Russian territory.

But Biden told reporters Monday that the U.S. will not "send to Ukraine rocket systems that can strike into Russia," and he and the administration are making efforts to emphasize that these new rocket systems will be used by the Ukrainians on the battlefield in their own country.

-ABC News' Conor Finnegan

Russia's invasion of Ukraine has left 5.2 million kids in need of humanitarian help, according to UNICEF.

At least 262 children have been killed and another 415 have been hurt since Feb. 24, UNICEF said.

Nearly two-thirds have been displaced, UNICEF said.

Russia's invasion of Ukraine has already engaged around 330,000 Russian personnel, Brigadier General Oleksiy Hromo of the General Staff of the Ukrainian Armed Forces told local media on Thursday.

“[Russian] groups at various axes are close to 150,000 strong. If we add their air and sea components, there are about 220,000 military personnel,” Hromo said. Russia also deployed “units of the national army combat reserve, the federal service of guard forces, and mobilization units,” the Brigadier General added.

Hromo's sobering account came on the back of claims made by a top Ukrainian official earlier on Wednesday that revealed mounting Ukrainian casualties. Up to 1,000 Ukrainian soldiers are being killed or wounded each day in the Donbas region of eastern Ukraine, with 200 to 500 killed on average and many more wounded, said David Arakhamia, who heads the presidential faction in the Ukrainian parliament.

In early June, Ukrainian President Volodymyr Zelenskyy said daily fatalities among Ukrainian ranks at the Donbas front were between 60 to 100 troops.

Arakhamia, one of Zelenskyy's closest advisers who oversees Ukraine's stalled negotiations with Russia, has been leading a Ukrainian delegation in Washington this week in a bid to lobby the Biden administration and Congress.

Arakhamia's team want to see the pace of weapons shipments increased and is pushing for a designation of Russia as a state sponsor of terrorism.

-ABC News' Edward Szekeres, Yuriy Zaliznyak, Yulia Drozd and Max Uzol