Moscow has said it will be forced to strengthen its defences in the Baltic if Finland and Sweden join Nato, including by deploying nuclear weapons, as the war in Ukraine entered its seventh week and the country braced for a major attack in the east.
However, the Lithuanian defence minister, Arvydas Anušauskas, claimed on Thursday that Russia already had nuclear weapons stored in its Baltic exclave of Kaliningrad, which borders Lithuania and Poland. That claim has not been independently verified, but the Federation of American Scientists (FAS) reported in 2018 that nuclear weapon storage bunkers in Kaliningrad had been upgraded.
The Russian former president Dmitry Medvedev, a senior member of Russia’s security council, said on Thursday that all its forces in the region would be bolstered if the two Nordic countries joined the US-led alliance.
Medvedev’s threat is the latest of many instances of nuclear sabre-rattling from the Kremlin aimed at deterring western military intervention on behalf of Ukraine.
“We’re obviously very concerned,” said the CIA director, William Burns. “Given the potential desperation of President Putin and the Russian leadership, given the setbacks that they’ve faced so far militarily, none of us can take lightly the threat posed by a potential resort to tactical nuclear weapons or low-yield nuclear weapons.”
But Burns added: “While we’ve seen some rhetorical posturing on the part of the Kremlin, moving to higher nuclear alert levels, so far we haven’t seen a lot of practical evidence of the kind of deployments or military dispositions that we would reinforce that concern.”
Finland and Sweden are deliberating over whether to abandon decades of military non-alignment and join Nato, with the two Nordic countries’ leaders saying Russia’s onslaught on Ukraine has changed Europe’s “whole security landscape”.
Their accession to the alliance would more than double Russia’s land border with Nato members, Medvedev said. “Naturally, we will have to reinforce these borders” by bolstering ground, air and naval defences in the region, he said.
Medvedev, a close ally of Vladimir Putin, explicitly raised the nuclear threat, saying Finnish and Swedish Nato membership would mean there could be “no more talk of any nuclear-free status for the Baltic – the balance must be restored”.
Russia had “not taken such measures and was not going to”, he said. “But if our hand is forced, well … take note it wasn’t us who proposed this.”
Russia borders the Baltic states of Estonia and Latvia, and the Russian exclave of Kaliningrad is sandwiched between Poland and Lithuania.
Russia’s deputy foreign minister, Alexander Grushko, said Moscow would take the security and defence measures that it would deem necessary if Sweden and Finland join Nato, adding that the move would seriously worsen the military situation and lead to “the most undesirable consequences”.
Anušauskas described the Russian threat as “rather strange” because, he said, nuclear weapons “have always been kept” in Kaliningrad. “They keep nuclear weapons, delivery vehicles, and have warehouses,” he told the Baltic News Service. “The international community and countries in the region are perfectly aware of that.”
In 2018 the FAS analysed satellite images and concluded that the Russians had carried out a major renovation of what appeared to be “an active nuclear weapons storage site in the Kaliningrad region”. However, the analysts were unable to determine whether nuclear warheads were already being stored there, were imminently about to arrive, or would be moved there in a crisis.
“There is indeed a storage site in Kaliningrad, known as Kolosovka. That is where nuclear weapons for all units located in Kaliningrad would be,” said Pavel Podvig, a military expert based in Geneva who runs a research project on Russian nuclear forces. “There are conflicting reports about whether Russia actually has any weapons in Kolosovka. We don’t really know.”
Hans Kristensen, the director of the nuclear information project at FAS, said work was still going on at the storage bunkers. “They’re working on security perimeter now. So I doubt there are warheads in there,” Kristensen said.
Finland’s prime minister, Sanna Marin, said on Wednesday that Finland, which shares an 810-mile (1,300km) border with Russia, was likely to decide on a Nato application “within weeks”, while her Swedish counterpart, Magdalena Andersson, said there was “no point delaying” the decision.
Ukraine’s president, Volodymyr Zelenskiy, said Russian forces who have pulled back from northern Ukraine after failing to take the capital were “increasing their activities on the southern and eastern fronts, attempting to avenge their defeats”.
The deputy defence minister, Hanna Malyar, said on Thursday that Russia was massing forces along the Russia-Ukraine border, in Belarus and in the breakaway Transdniestria region of Moldova, with the eastern cities of Kharkiv, Donetsk and Zaporizhzhia coming under missile attack.
Moldova accused the Russian army of trying to recruit its citizens after British military intelligence said Moscow was attempting to enlist fighters in Transdniestria, a narrow strip of land held by pro-Russia separatists that is within about 25 miles of the Ukrainian port of Odesa.
“Such actions do not promote peace for all of us, our fellow citizens, for our families. Such things are very dangerous and they must be stopped,” said the Moldovan foreign minister, Nicu Popescu, without giving further details. The Kremlin did not immediately comment.
The chief military development of the day was the loss of Russia’s flagship missile cruiser, Moskva, which sank in “stormy seas” while being towed to a port in the Black Sea after an explosion.
The Ukrainian southern military command claimed late on Wednesday to have struck the Moskva with Neptune anti-ship cruise missiles, while distracting its crew with an aerial drone, causing it to start sinking and forcing the crew to abandon ship.
Russia’s defence ministry initially denied reports that it had sunk and claimed the fires had been extinguished. Four Russian ships that had gone to the Moskva’s rescue were being hampered by stormy weather and by ammunition blowing up onboard, it said.
But late on Thursday, the ministry said in a statement: “The cruiser ship Moskva lost its stability when it was towed to the port because of the damage to the ship’s hull that it received during the fire from the detonation of ammunition. In stormy sea conditions, the ship sank.” The crew had been safely evacuated, but it marks the most significant military loss of a naval vessel since the Argentinian cruiser the General Belgrano was torpedoed by a British submarine in 1982.
Moscow said the port of Mariupol was under its full control, but Vadym Denysenko, an adviser to Ukraine’s interior minister, said on Thursday that the battle over the seaport was “still ongoing today”.
Mariupol is a key target in Moscow’s push to secure a land corridor between the self-proclaimed republics in Donetsk and Luhansk in Donbas and Crimea, which Russia occupied and annexed in 2014, and its capture would allow the Kremlin’s military planners to redeploy vital resources farther east.
Russian officials accused Ukraine of using helicopters to bomb a town in the southern Bryansk region, about 6 miles from the border, saying seven people were injured in shelling and describing the attack as a “deliberate strike on residential buildings”. The claim could not be independently verified.
The Russian retreat from around Kyiv has led to the discovery of large numbers of apparently massacred civilians, drawing international condemnation and calls for a war crimes investigation. The Hague-based international criminal court, which deals with rights abuses, said Ukraine had become a “crime scene”.
The ICC’s chief prosecutor, Karim Khan, said on a visit to Bucha, where officials say more than 400 civilians died: “We’re here because we have reasonable grounds to believe that crimes within the jurisdiction of the court are being committed.” Moscow has rejected all reports of atrocities, which Putin has dismissed as “fakes”.
• This article was amended on 15 April 2022 to better characterise Kaliningrad as an exclave, rather than an enclave.
