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

A Moscow court has sentenced one of Russia's best-known opposition leaders, whose family live in the U.S., to 25 years in prison in what is widely seen a show trial.

Vladimir Kara-Murza is the most high-profile opponent of Russian President Vladimir Putin to be jailed since Alexey Navalny.

Kara-Murza's extraordinarily harsh sentence is one of the lengthiest any opposition figure has received under Putin and illustrates how repressive Russia has become during the war in Ukraine, reverting to something much closer to the USSR where no opposition is tolerated.

Kara-Murza was convicted of treason, as well as "discrediting Russia's armed forces," a new law that effectively criminalizes criticizing the war in Ukraine. He was also convicted of belonging to a banned organization. The charges are widely seen as politically motivated.

Kara-Murza is one of Russia's best-known pro-democracy figures and a veteran critic of Putin.

Kara-Murza, who holds both British and Russian citizenship, spent many years living in the United States and his wife and children still live in Virginia. He was close to the late U.S. Sen. John McCain, who championed human rights in the former Soviet Union.

Dozens of journalists and Western diplomats attended the court hearing on Monday, including the U.S. ambassador who read out a statement condemning the sentence.

"We support Mr. Kara-Murza and every Russian citizen to have a voice in the direction of their country. Mr. Kara-Murza and countless other Russians believe in and hope for a Russia where fundamental freedoms will be upheld. And we will continue to share those hopes and work for that outcome," Amb. Lynne Tracy said.

Kara-Murza previously has survived being poisoned not once but twice. In 2015 and then again in 2017, he suffered organ failure after being exposed to an unknown toxin. Independent researchers later linked the poisoning to the same team of FSB poisoners who targeted Navalny.

He chose to return to Russia after the war began, believing it was important to continue to campaign for freedom in his country and has been an outspoken critic of the invasion.

His trial was held entirely behind closed doors, but a letter containing his closing statement to the court has been released to reporters.

"I only blame myself for one thing," Kara-Murza said in the statement. "I failed to convince enough of my compatriots and politicians in democratic countries of the danger that the current Kremlin regime poses for Russia and for the world."

"Criminals are supposed to repent of what they have done. I, on the other hand, am in prison for my political views. I also know that the day will come when the darkness over our country will dissipate.

-ABC News' Patrick Reevell