Ukrainian President Volodymyr Zelenskyy announced Wednesday the Security Service of Ukraine and the police arrested a suspect who they say coordinated with Russian forces in Tuesday's missile attack on Kramatorsk, a city in the Donetsk region.

The missiles struck a popular pizzeria and killed 12 people, including three children. More than 60 people were injured, the president said in a public address.

The unidentified "spotter" was charged with treason, according to Zelenskyy.

"Anyone in the world who does not understand that one cannot be an accomplice of a terrorist state must be held accountable by the entire international community," he said.

-ABC News' Will Gretsky

A senior U.S. official tells ABC News that Yevgeny Prigozhin thought he would have help from the Russian military.

Both former Russian military officers and some others in Moscow had conversations with Prigozhin before he started his march, the official said.

The U.S. doesn't believe Russian President Vladimir Putin realized this beforehand, and the officers sided with Putin in the end, the official said.

According to the official, Prigozhin was shocked he didn’t have support.

-ABC News' Martha Raddatz

Two Russian missiles struck Kramatorsk, a city in Ukraine's Donetsk region, killing at least four people, according to officials.

At least 47 people were injured in the attack, but the death and injury toll could rise.

One of the deceased victims was a 15-year-old and one of the wounded victims was a child under a year-old, officials said.

One missile struck an eatery downtown and the other one hit the outskirts of the city, Andriy Yermak the head of the Ukrainian Presidential Office said.

A restaurant and a hotel were badly damaged as a result of the strikes, according to officials.

Crews continued to dig through the rubble to search for victims throughout the evening.

"Each such manifestation of terror proves over and over again to us and to the whole world that Russia deserves only one thing as a result of everything it has done - defeat and a tribunal, fair and legal trials against all Russian murderers and terrorists," Ukrainian President Volodymyr Zelenskyy said in a statement.

-ABC News' Fidel Pavlenko and Ellie Kaufman

The U.S. announced additional sanctions targeting the Wagner Group, specifically going after gold companies and a Russian man it says are illicitly funding the Wagner Group’s operations in Ukraine and Africa.

Central African Republic based companies Midas Resources SARLU and Diamville SAU, Dubai based company Industrial Resources General Trading and Russia based company Limited Liability Company, re connected to Wagner’s leader Yevgeny Prigozhin, who is already subject to U.S. sanctions along with numerous other entities linked to the Wagner Group, according to the Department of the Treasury’s Office of Foreign Assets Control.

Andrey Nikolayevich Ivanov, a Russian national, and an executive in the Wagner Group, allegedly worked closely with Prigozhin’s entity Africa Politology and senior Malian government officials on weapons deals, mining concerns, and other Wagner Group activities in Mali, OFAC said.

"The Wagner Group funds its brutal operations in part by exploiting natural resources in countries like the Central African Republic and Mali," Brian Nelson, the U.S. under secretary of the treasury for terrorism and financial intelligence, said in a written statement. "The United States will continue to target the Wagner Group’s revenue streams to degrade its expansion and violence in Africa, Ukraine, and anywhere else."

-ABC News' Ben Gittleson

The United States "is prepared to defend every inch of NATO territory," National Security Advisor Jake Sullivan said Wednesday, amid Russia's threats of military retaliation if Sweden and Ukraine officially join the alliance.

"At the end of the day, Russia does not get a vote in who joins NATO," Sullivan told ABC News' George Stephanopoulos during an interview Wednesday on "Good Morning America."

"If Russia does choose to test Article 5, President Biden has said he is prepared to defend every inch of NATO territory," he added. "And later tonight, when he addresses a large crowd in Vilnius in a speech about his vision for Euro-Atlantic security and for American leadership, he will reinforce this point about the sanctity of Article 5."

Article 5 of the NATO treaty states that the signed parties "agree that an armed attack against one or more of them in Europe or North America shall be considered an attack against them all."

Sweden and Finland, which have historically embraced neutrality, applied for NATO membership together last year despite warnings from Moscow against doing so, as Russian forces invaded Ukraine. Finland officially joined the alliance in April following Turkish ratification, but Turkey and Hungary have yet to ratify Sweden’s membership. NATO Secretary-General Jens Stoltenberg announced Monday that Turkish President Recep Tayyip Erdogan has agreed to send Sweden’s NATO accession documents to Turkey’s Parliament for approval "as soon as possible," one of the last steps in the membership process.

Meanwhile, Ukraine is pushing hard for NATO membership as Russia’s war presses on. Stoltenberg announced Tuesday that the bloc "will issue an invitation for Ukraine to join NATO when allies agree and conditions are met," pledging to speed up the process by eliminating bureaucratic hurdles, but without offering a timeline.

"All 31 allies got together yesterday to say with one voice that Ukraine's future is in NATO. The real question is just how we work down the pathway to get them in," Sullivan told ABC News on Wednesday. "So the signal that NATO sent yesterday was very positive to Ukraine about its future prospects for joining NATO, and we will work in terms of the democratic and security sector reforms that are necessary. And in the meantime, we're not just going to sit around. We're going to provide Ukraine with the weapons and military assistance it needs to defend its territory against Russia and to deter future aggression from Russia."

Ukraine has requested F-16 fighter jets and long-range missiles to aid its counteroffensive against Russian forces. Sullivan said the U.S. has already taken steps with NATO allies to begin the training of Ukrainian pilots on F-16s, which "will take some time," and then the aircraft will be transferred to Ukraine "likely from European countries that have excess F-16 supplies." As for the long-range missiles, Sullivan said the U.S. will continue to look into the issue and discuss it with Ukraine.