Ukraine said on Monday that Russia was preparing for a fresh wave of missile attacks on its energy grid that have plunged swathes of the country into the cold and dark.
The warning came as foreign ministers from several European countries, including NATO-hopefuls Finland and Sweden, arrived in Kyiv.
A Ukraine military spokesman said a Russian warship capable of firing cruise missiles had recently deployed to the Black Sea with Kalibr-type missiles on board.
"This indicates that preparations were underway," said spokeswoman Natalia Gumeniuk.
"It's quite likely that the beginning of the week will be marked by such an attack," she added.
With temperatures dipping below zero, Ukraine said that repeated Russian attacks have left Ukraine's energy grid teetering on the brink of collapse and have disrupted power and water supplies to millions over recent weeks.
Russia fired dozens of cruise missiles at targets across Ukraine last week, and an official in Kyiv said Monday that residents in and around the capital were still suffering disruptions as a result.
Ukraine's President Volodymyr Zelenskyy cautioned in an address to Ukrainians late on Sunday that Russia was preparing new aerial attacks.
Russia has denied such claims and insisted that it only targets military-linked infrastructure facilities and blamed the blackouts and their civilian impact on Kyiv's refusal to negotiate with Moscow.
"Damage to residential buildings and civilian casualties are really happening because of the Ukrainian air defenses, which are deployed not in cities' suburbs, but rather in [city] centers," Russia's permanent representative to the UN, Vassily Nebenzia, was quoted as saying by Russia Today on Monday.
Nebenzia noted last Wednesday that the buildings had been hit with "American air defense missiles supplied to Kyiv."
The Ukraine presidency said Monday that Russian strikes had left four people dead in frontline regions a day earlier.
Prime Minister Denys Shmygal meanwhile announced that he had received the foreign ministers of the three Baltic states, Latvia, Lithuania, Estonia, as well as those from Finland, Norway, Sweden and Iceland.
He said the country representatives had "discussed the tightening of sanctions, the reconstruction of energy infrastructure and financial support."
