The Wall Street Journal said on Thursday that it "vehemently denies" the spying allegations brought by Russia's intelligence service against its reporter.

"The Wall Street Journal vehemently denies the allegations from the FSB and seeks the immediate release of our trusted and dedicated reporter, Evan Gershkovich," a spokesperson for the WSJ said in a statement to ABC News. "We stand in solidarity with Evan and his family."

The FSB said it detained Gershkovich in the city of Ekaterinburg, in central Russia, and accused him of collecting "state secrets" on an enterprise belonging to Russia's military industrial complex on behalf of the United States.

Russia's FSB intelligence agency said on Thursday it had detained a journalist working for The Wall Street Journal on spying charges.

Russian state media cited an FSB statement saying Evan Gershkovich was detained in Ekaterinburg, a city in central Russia, and accusing him of collecting "state secrets" on an enterprise belonging to Russia's military industrial complex on behalf of the United States.

A criminal case has been opened against him, the officials said.

"It is established that Evan Gershkovich, acting on the instruction of the American side, was collecting information consisting of state secrets, about the activity of one of the enterprises of the Russian military industrial complex. He was arrested in Ekaterinburg during an attempt to receive secret information," Russian media said, quoting FSB officials.

Earlier reports from local media said that Gershkovich had been in Ekaterinburg reporting on the Wagner private military company.

Gershkovich is a reporter for the WSJ covering Russia, Ukraine and the former Soviet Union. He previously reported for Agence France-Presse and The Moscow Times, according to his WSJ profile. He also served as a news assistant at The New York Times.

-ABC News Tanya Stukalova and Patrick Reevell

The U.S. will support the creation of a special tribunal to prosecute top Kremlin officials for Russia's aggression toward Ukraine, State Department officials said Tuesday, marking a significant shift for the Biden administration and a notable step toward outlining what accountability on the international stage might look like after the conflict.

A department spokesperson said the administration envisioned the tribunal would take the form of an international court that is "rooted in Ukraine's judicial system" but ideally located in another European country.

The spokesperson added that such a mechanism would work to "facilitate broader international support and demonstrate Ukraine's leadership in ensuring accountability for the crime of aggression" as well as "maximize the chances of achieving meaningful accountability for the crime of aggression."

Ukraine and other Western countries have long called for a special tribunal, but until now, the U.S. has not publicly declared if it would support the creation of a new structure.

-ABC News' Shannon K. Crawford

At least two people were killed and 29 were injured Monday morning when a pair of long-range Russian missiles slammed into buildings in a city in eastern Ukraine, Ukrainian officials said.

The two S-300 Russian missiles hit administrative and office buildings, and private homes in Sloviansk, according to Pavlo Kyrylenko, the regional governor.

Sloviansk is in the Donetsk region of eastern Ukraine, where heavy fighting has been waged since the start of the war.

The missiles struck the city around 10:30 a.m. local time, Kyrylenko said.

He said the town of Druzhkivka in the Donetsk region was also targeted in Monday's missile attacks. Kyrylenko said a Russian missile "almost completely destroyed" an orphanage in Druzhkivka, but there were no immediate reports of casualties.

"Another day that began with terrorism by the Russian Federation," Ukrainian President Volodymyr Zelenskyy said in a statement.

Zelenskyy said Ukraine "will not forgive the torturing of our people."

"All Russian terrorists will be defeated," Zelenskyy said. "Everyone involved in this aggression will be held to account."

ABC's Will Gretsky

The leader of of Russia's Wagner mercenary group appeared on Sunday to ditch plans to withdraw his forces from Bakhmut in eastern Ukraine after receiving promises overnight that they would get all the arms needed to capture the devastated city.

Yevgeny Prigozhin said in a new audio message that the Kremlin has promised to resupply his Wagner Private Military Company with as much ammunition and weapons as they need.

Prigozhin said that for the first time he received a response to the situation regarding the shortage of ammunition. He said on Saturday night that the relevant companies promised to deliver everything necessary to continue the offensive in Bakhmut.

"Overnight we received a combat order, for the first time in all this time," Prigozhin said. "We have been promised as much ammunition and weapons as we need to continue further operations. We have been promised that everything needed to prevent the enemy from cutting us off (from supplies) will be deployed on the flank," he added.

In addition, Russian Army Gen. Sergei Surovikin will personally deal with issues of interaction between the Wagner PMC and the Ministry of Defense, Prigozhin said. "This is the only man with the star of an army general who knows how to fight," Prigozhin said of the Russian Defense Ministry assigning Surovikin to work alongside Wagner.

Surovikin commanded Russia's Ukraine campaign for several months before the chief of the General Staff, Army Gen. Valery Gerasimov, was given overall operational command above him.