Russia-Ukraine updates: Russian missiles hit close to nuclear reactors: IAEA director

Attorney General Merrick Garland made an unannounced visit to Ukraine on Tuesday.

Garland is meeting with Ukrainian Prosecutor General Iryna Venediktova to discuss the efforts to help identify, apprehend and prosecute the people involved in war crimes and other atrocities in Ukraine, a Department of Justice official said.

Garland told reporters, "The United States is sending an unmistakable message: There is no place to hide. We and our partners will pursue every avenue available to ensure that those who are responsible for these atrocities are held accountable."

Garland announced that the Justice Department has launched a War Crimes Accountability Team.

"This initiative will bring together the Department’s leading experts in investigations involving human rights abuses and war crimes and other atrocities; and provide wide-ranging technical assistance, including operational assistance and advice regarding criminal prosecutions, evidence collection, forensics, and relevant legal analysis," the department said in a statement. "The team will also play an integral role in the Department’s ongoing investigation of potential war crimes over which the U.S. possesses jurisdiction, such as the killing and wounding of U.S. journalists covering the unprovoked Russian aggression in Ukraine."

The Justice Department also said it will provide more personnel to help Ukraine and other international partners counter Russian illicit finance and sanctions evasion, including "an expert Justice Department prosecutor to advise on fighting kleptocracy, corruption, and money laundering."

-ABC News' Alex Mallin

U.S. citizen Stephen Zabielski has died in Ukraine, the State Department confirmed to ABC News Tuesday morning.

"We can confirm the death of U.S. citizen Stephen Zabielski in Ukraine," a State Department spokesperson said. "We have been in touch with the family and have provided all possible consular assistance. Out of respect to the family during this difficult time, we have nothing further."

Zabielski's death was first reported by Rolling Stone.

US officials again cautioned Americans against traveling to Ukraine, saying "that U.S. citizens in Ukraine should depart immediately if it is safe to do so using any commercial or other privately available ground transportation options."

-ABC News' Matthew Seyler

Following Ukraine's attack on three oil drilling platforms in the Black Sea off the coast of Russian-annexed Crimea on Monday, Russian officials announced plans to strike critical Ukrainian targets in retaliation.

“The attack on the Chernomorneftegaz towers unleashes Russia's hands,” Mikhail Sheremet, a Russian member of parliament, said on Monday as quoted by Russian media. “Retaliatory strikes on decision-making centers will be carried out in the near future,” Sheremet added.

Seven people remain missing after Ukraine's strike on the drilling platforms, a source in the emergency services of Crimea said on Tuesday.

The fire on one of the oil rigs is still continuing, Russian Federation Council member from Crimea Olga Kovitidi told Interfax.

"With regards to the blaze, it is not abating on the oil rig. The fire approached the well overnight," Kovitidi said.

On a day filled with intimidation tactics, Russia extended its threats to Lithuania on Monday, calling the Baltic country's decision to suspend the transit of EU-sanctioned goods to the Russian Kaliningrad region “unprecedented” and “illegal."

On June 18, Lithuania notified the Kaliningrad Railway of suspending the transit of EU-sanctioned goods through its territory. Up to half of ready-to-import goods, including building materials and metals, are subject to the ban, Kaliningrad region Governor Anton Alikhanov said.

The Russian Foreign Ministry summoned the Lithuanian Chargé d'Affaires on Monday and warned the Baltic diplomat of repercussions if freight transit to the Kaliningrad region is not restored in full in the near future.

“Russia reserves the right to take action to protect its national interests,” the Russian ministry told the Lithuanian official as reported by local media.

Ukrainian Foreign Minister Dmytro Kuleba said in a tweet on Monday that “Russia has no right to threaten Lithuania.” According to Kuleba, “Moscow has only itself to blame for the consequences of its unprovoked and unjustified invasion of Ukraine.”

Yet on the same day, Russian officials announced military drills of the Baltic Fleet in the Kaliningrad region.

Several hundred firings of multiple rocket launcher systems, large-caliber guns and other artillery will be carried out during the exercises, the Baltic Fleet stated on Monday.

Maneuvers in the Kaliningrad region on Monday involved about 1,000 servicemen and more than 100 combat units, including special artillery equipment and missile units, according to Russian media.

Andriy Yermak, who heads the Ukrainian Presidential office, said Russia's attempts to threaten Lithuania “are a challenge for the European Union and NATO.”

“Now it is important to maintain a stable position and not make concessions to Russia on sanctions and restrictions on the transit of goods from Russia to Kaliningrad,” Yermak said on Monday.

Any concession will be perceived by Russia as a weakness, the Ukrainian official added.

-ABC News' Edward Szekeres, Max Uzol, Tatiana Rymarenko and Yuriy Zaliznyak

Kremlin spokesperson Dmitry Peskov told MSNBC that Americans Andy Tai Ngoc Huynh and Alexander Drueke, who were captured while fighting in Ukraine, "committed crimes," and that they were not part of the Ukrainian armed forces and therefore not subject to the Geneva Conventions.

"They were involved in firing and shelling our military personnel, they were endangering their life and they should be responsible. They should be held responsible … for those crimes that they have committed," he said.

The Geneva Conventions outline the humanitarian rights given to prisoners of war, however, mercenaries are not given the same protections.

Regarding WNBA star Brittney Griner, who has been detained in Russia since February, Peskov said she’s not a hostage.

He said Russia has strict drug laws and she was caught carrying banned substances.

Griner was taken into custody at an airport near Moscow after officials allegedly found vape cartridges with hashish oil in her bag. Hasish oil is illegal to possess in Russia. The U.S. government has classified her case as "wrongfully detained," which means that the U.S. would work to negotiate her release.