Russia-Ukraine updates: 2 US veterans who joined Ukrainian forces missing

United Nations Secretary-General Antonio Guterres admitted Thursday that "the U.N. Security Council has not been able to do everything in its power" to resolve the war in Ukraine, as he pledged to "fight with the use of force."

"We will not give up," Guterres said during a joint press conference with Ukrainian President Volodymyr Zelenskyy in Kyiv.

According to Guterres, U.N. staff are already providing on-site assistance in 30 locations across Ukraine. The U.N. chief called Russia's invasion of Ukraine "a violation of the U.N. Charter." One of the organization's values, he said, "is the need that territorial integrity of the countries must be respected."

"This is fundamental," Guterres added.

Guterres visited Kyiv as the Ukrainian capital was hit by two missile strikes on Thursday evening. Five missiles flew into the city, according to Zelenskyy. At least 10 people were injured, including four who were hospitalized, according to the Kyiv City Council.

"This says a lot about Russia's true attitude to global institutions. About the efforts of the Russian leadership to humiliate the U.N. and everything that the organization represents," Zelenskyy said in his nightly broadcast.

Earlier on Thursday, Russian Foreign Ministry spokesperson Maria Zakharova accused Western countries of openly calling on Ukraine to attack Russian territory with the weapons they supply to Kyiv.

"We have already commented the other day on statements by British Deputy Defense Minister [James] Heappey about okaying Ukraine's strikes on Russian military targets," Zakharova told reporters in Moscow, according to Russian state media. "In other words, the West is openly calling on Kiev to attack Russia, even with weapons received from NATO countries."

According to Zakharova, Kyiv has taken this as a guide to action, evidenced by the Ukrainian military's shelling of Russian border territories over the past few weeks that resulted in casualties and destruction. Zakharova said the Ukrainian strikes were "further evidence that Zelenskyy's regime is not independent in its decisions and is completely dependent on external handlers."

Zakharova also stressed that such "criminal activity" of the Ukrainian military against Russian territory cannot go unanswered.

"I would like Kyiv and Western capitals to take seriously the statements of our country's defense ministry that further Ukrainian provocations to strike Russian targets will definitely lead to a harsh response from Russia," she said.

At a press conference in Vienna on Thursday, International Atomic Energy Agency Director-General Rafael Grossi warned that Russian missiles over Ukrainian power plants could cause a nuclear accident. Grossi, who recently visited Ukraine and its Chernobyl nuclear power plant, said the Ukrainian government officially informed his agency, the nuclear watchdog of the U.N., of a video surveillance camera recording the flight of a missile directly over the South Ukraine nuclear power plant near the city of Yuzhnoukrainsk on April 16.

"The IAEA is studying the evidence and if it is confirmed, the incident will have extremely serious consequences," Grossi said. "If such a missile changed its trajectory, it could seriously affect the physical integrity of the nuclear power plant, which could lead to a nuclear accident."

-ABC News' Edward Szekeres, Yuriy Zaliznyak, Uliana Lototska and Nataliia Kushnir

The U.S. has "credible information" that Russia could be "intensifying" the forced displacement of civilians as it plans to overthrow local governments in southern and eastern Ukraine, a senior U.S. diplomat said Thursday.

Michael Carpenter, the U.S. Ambassador to the Organization for Security and Cooperation in Europe, told reporters there is "credible reporting" that after failing to topple the central government in Kyiv, Russian forces are forcibly removing Ukrainian civilians from areas in the south and east -- and could be "intensifying" those efforts as they seek to set up proxy local governments.

Carpenter said he has also now deemed "credible" the reports that Russian forces are forcibly displacing Ukrainian civilians, often through "filtration camps" where many are "brutally" interrogated, to tamp down on Ukrainian support in these parts of the war-torn country.

Carpenter repeatedly declined to provide more details to back up these claims, saying only, "We have very credible information from a variety of different sources that point to Russia's plans."

-ABC News' Conor Finnegan

The House voted 417-10 approving a measure that will make it easier for the U.S. to send military aid and equipment to Ukraine.

The Senate approved the measure by voice vote last month. It now heads to President Joe Biden's desk for his signature.

The lend-lease program was created during WWII and was seen as a game-changer in the conflict, allowing the U.S. to quickly resupply Allies.

This enhanced lend-lease authority would be specific to helping remove obstacles to lending arms to Ukraine. It would not create a new program but would streamline the president’s current authority to lend the defense articles necessary to defend civilian populations.

The legislation would also require Biden to establish expedited delivery procedures for any military equipment loaned or leased to Ukraine to ensure timely delivery.

It would remain in effect for two years with the possibility of Congress extending the authority if needed.

-ABC News' Mariam Khan

Kyiv Mayor Vitali Klitschko said Ukraine's capital was hit by two missile strikes in the Shevchenkivsky district on Thursday.

At least one Russian missile struck a residential building. Anton Gerashchenko, an adviser to the interior minister who was at the scene following the attack, told journalists at least six people were injured.

This came as United Nations Secretary-General Antonio Guterres visited the city.

Mykhailo Podolyak, adviser to Ukrainian President Volodymyr Zelenskyy, tweeted that the attack came right after Guterres visited Russia.

"The day before he was sitting at a long table in the Kremlin, and today explosions are above his head. Postcard from Moscow? Recall why [Russia] still takes a seat on the UN Security Council?" he tweeted.

This was the first strike on central Kyiv in over a week.

-ABC News' Patrick Reevell