Moscow warned Lithuania of "serious" consequences on Tuesday over its restriction of rail traffic to Russia's Kaliningrad exclave, as Kremlin forces made gains in Ukraine's strategic Donbas region.

Kremlin troops were causing "catastrophic destruction" in Lysychansk, an industrial city at the forefront of clashes in the eastern Donbas, the region's governor said. Ukraine confirmed Russia had taken frontline village Toshkivka.

Governor Sergiy Gaiday said "every town and village" in Ukrainian hands in Lugansk region was "under almost non-stop fire".

Since being repelled from Kyiv and other parts of Ukraine following its invasion in February, Moscow is focusing its offensive on the strategic Donbas region.

In the eastern town of Sloviansk, which could become a flash point as Russian troops advance from the north, local people were preparing to withstand attack and the authorities said the community would defend itself.

"We believe they'll beat the Russian scum," resident Valentina, 63, said of local Ukrainian forces.

The stakes are high. The town was seized by Russia-backed separatists in 2014 and then retaken by Ukrainian forces after a lengthy siege.

'Serious' consequences

Russia's war of words with EU member Lithuania escalated on Tuesday, vowing "serious" consequences over Vilnius' restrictions on rail traffic to the exclave of Kaliningrad.

Lithuania says it is simply adhering to EU-wide sanctions on Moscow but Russia countered, accusing Brussels of "escalation".

Moscow summoned the EU's ambassador to Russia. Its foreign ministry said Lithuania's actions "violate the relevant legal and political obligations of the European Union".

On the ground, the police chief of the Kyiv region said victims of the Russian attempt to seize the capital city continued to be found. So far, the bodies of 1,333 civilians have been discovered and 300 people still missing.

On the maritime front, Russia's navy is blockading ports, which Ukraine says is preventing millions of tonnes of grain from being shipped to world markets, contributing to soaring food prices.

Prior to the war, Ukraine was a major exporter of wheat, corn and sunflower oil.

With European officials due to gather this week at a summit expected to approve Ukraine's candidacy to join the EU, Brussels foreign policy chief Josep Borrell called the Russians' port blockade "a real war crime".

He said it was happening "while in the rest of the world people are suffering hunger".

Moscow denies responsibility for the disruption to deliveries and, following Borrell's comments, blamed the West's "destructive" position for surging grain prices.

Growing concerns about a food crisis are "the fault of Western regimes, which act as provokers and destroyers", said foreign ministry spokeswoman Maria Zakharova.

Ukrainian President Volodymyr Zelensky said Kyiv was engaged in "complex negotiations" to unblock grain exports, although he cautioned that there was no progress as yet.

In an address to the African Union, he said the continent was a "hostage" of the conflict, and rising food prices had "already brought (the war) to the homes of millions of African families".

The EU has pledged an additional 600 million euros ($635 million) to help vulnerable nations weather the food security crisis.

'Significant losses'

In addition to Toshkivka, Ukraine said it had lost control of the eastern village of Metyolkine, a settlement adjacent to Severodonetsk, which has been a focus of fighting for weeks and is now largely under Russian control.

A chemical plant in Severodonetsk where hundreds of civilians are said to be sheltering was being shelled constantly, Ukraine warned.

But defence ministry spokesman Oleksandr Motuzyanyk told Ukrainian television that Russian forces had suffered "significant losses in the area of Severodonetsk".

"They are fighting under the old statutes of the Soviet era. This is a war for territory," he said.

Three people were injured and seven more missing after Ukrainian forces attacked oil drilling platforms in the Black Sea off the coast of Crimea, which was annexed by Russia in 2014, Crimea's Moscow-backed leader Sergey Aksyonov said.

It was the first reported strike against offshore energy infrastructure in Crimea since Russia launched its invasion and Russian lawmaker Olga Kovitidi said the complex was still ablaze.

$100 million medal

In New York, Dmitry Muratov, the Russian editor-in-chief of the independent newspaper Novaya Gazeta, auctioned off his Nobel Peace Prize gold medal for $103.5 million to benefit children displaced by the war.

It was sold to an as yet unidentified phone bidder.

Muratov, who won the prize in 2021 alongside journalist Maria Ressa of the Philippines, and others at the auction were stunned when the final bid came in at tens of millions of dollars more than the previous offer.

With US-Russia tensions soaring, Kremlin spokesman Dmitry Peskov told NBC News that two Americans captured in Ukraine while fighting with Kyiv's military were "endangering" Russian soldiers and should be "held accountable for those crimes".

The interview is the first time the Kremlin has commented on the cases of Alexander Drueke and Andy Huynh, both US military veterans, according to NBC.

Spain said one of its citizens fighting for Ukraine had been killed in the country without giving further detail.

Denmark meanwhile became the latest European country to warn of potential gas supply problems. Its energy agency issued an early warning, due to uncertainty over hydrocarbon imports from Russia.