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

The United Kingdom announced a new wave of sanctions on Thursday targeting Russians involved in the barbaric treatment of children in Ukraine.

Maria Lvova-Belova, Russia's Children Rights Commissioner, tops the new list of sanctioned individuals for her alleged involvement in the forced transfer and adoption of Ukrainian children. She has been accused of enabling 2,000 vulnerable children being violently taken from the Luhansk and Donetsk regions and orchestrating a new policy to facilitate their forced adoptions in Russia.

“Today we are targeting the enablers and perpetrators of [Russian President Vladimir] Putin’s war who have brought untold suffering to Ukraine, including the forced transfer and adoption of children,” U.K. Foreign Secretary Liz Truss said in a press release.

More than 900 children were injured in Ukraine as a result of the full-scale armed aggression by the Russian Federation, according to the Ukrainian Prosecutor General’s latest report. Over 320 children were killed and more than 580 were injured.

These figures are far from being final, with more information slowly trickling in from places of active hostilities, as well as the temporarily occupied and liberated territories.

The UK's sanction list also includes Patriarch Kirill, the head of the Russian Orthodox Church, for his support and endorsement of Putin’s war.

Several members of Putin's political elite, along with four Military Colonels from a unit known to have killed, raped and tortured civilians in the Ukrainian town of Bucha, appear on the list too.

“Putin’s allies continue to choose to turn a blind eye to alleged war crimes and support his bloody offensive,” the U.K. government said. With Putin’s aggression reaching beyond Ukraine as Russian exports fuel conflict across the globe, the official press release read, the new sanctions also hit Myanmar’s military Junta.

The Junta relies heavily on Russian air assets and limiting it will cut Putin off from profiting from sales that fund his war machine, the U.K. said.

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

The State Department has still not confirmed reports that two former U.S. service members who volunteered to help Ukrainian forces have gone missing, spokesperson Ned Price said Thursday.

The Americans, Andy Tai Ngoc Huynh and Alexander Drueke, are both from Alabama.

"We are limited in terms of what we know at the moment," Price said. "We're closely monitoring the situation we are in contact with Ukrainian authorities, as well as with the International Committee of the Red Cross, and the families of the two reported missing U.S. citizens."

The department has not "seen anything from the Russians indicating that two such individuals are in their custody," Price said.

"If the Russians were to claim that they had such individuals, I assume we would pursue that. If we had reason to believe -- credible reasons to believe -- that these individuals were in Russian custody, we would pursue that as appropriate," Price continued.

Price was asked whether the department was tracking any other cases of Americans purportedly captured on the battlefield, and he said the department was aware of reports about "one additional American whose whereabouts are unknown.”

"Similarly, our understanding was that this individual had traveled to Ukraine to take up arms," Price said. He said the person was identified as missing "in recent weeks" and that the State Department was also in contact with their family.

Alabama Rep. Terri Sewell said that Drueke’s mother reached out to her office after losing contact with him. Sewell is helping the family locate him. Alabama Rep. Robert Aderholt said his office is helping in the search for Huynh after his family reached out to the congressman's office this week.

-ABC News' Shannon Crawford

In the first visit of EU leaders to the Ukrainian capital since Russia’s invasion, German Chancellor Olaf Scholz, French President Emmanuel Macron, Italian Prime Minister Mario Draghi and Romanian President Klaus Iohannis made clear their message of support and solidarity.

Scholz said, "My colleagues and I came here to Kyiv today with a clear message: Ukraine belongs to the European family."

Macron added, "All four of us support [Ukraine's] immediate EU candidacy."

The leaders discussed the possibility of further sanctions against Russia as well as how to rebuild Ukraine after the war.

Earlier in the day, the EU leaders toured Irpin, a town northeast of Kyiv, which was hit by heavy Russian artillery early in the war.

-ABC News' Britt Clennett and Ibtissem Guenfoud

Russian President Vladimir Putin hinted at the possibility of nuclear warfare during his Wednesday address to the council of legislators.

"If someone from outside moves to interfere in the current developments, they should know that they will indeed create strategic threats to Russia, which are unacceptable to us, and they should know that our response to encounter assaults will be instant, it will be quick," Putin said, according to Russian state media.

Putin claimed Russia's response to strategic threats from outside Ukraine would be “immediate."

“We have all the tools to do it, tools that others can't boast of at the moment, but as for us, we won't be boasting,” Putin said.

Putin said that Russia is prepared to use those “tools” if “the need arises," adding that he “would like everyone to be aware of it.” A nuclear attack has been on the table since the onset of the “special military operation” in Ukraine, Putin said. He had ordered his nuclear forces to be put on high alert on Feb 27.

Putin's remarks came as Pentagon press secretary John Kirby announced that “more than half” of the 90 howitzers the U.S. agreed to send to Ukraine were now in the country, adding that around 50 Ukrainian troops have already been trained to operate the weapons.

“We finished up earlier this week, the first tranche of more than 50 trainers that are going to go in and train their teammates,” Kirby said during a press briefing on Wednesday, a moment later adding, “But there was another tranche of more than 50 that we're going to go through training in the same location outside Ukraine.”

The U.S. Department of Defense on Wednesday tweeted pictures of more howitzers “bound for Ukraine” that were being loaded onto US Air Force aircraft. Additional training opportunities on Howitzers and other weapons systems were also being explored, Kirby said.

As U.S. weapons head to Ukraine, Russia is increasing the pace of its offensive in almost all directions, the General Staff of the Ukrainian Armed Forces said on Thursday.

The U.S. is considering the legal aspects of officially listing Russia as a state-sponsor of terrorism, Secretary of State Anthony Blinken told lawmakers on Wednesday. Officials said they haven't yet determined whether Russia's actions meet the legal standard required for the designation, Blinken said.

The designation, called for by Ukrainian President Volodymyr Zelenskyy and Foreign Minister Dmytro Kuleba, would further cripple Russia's trade potential, including bans on defense exports and limits on foreign aid.

-ABC News’ Edward Szekeres, Uliana Lototska and Fidel Pavlenko