Finland is expected to announce on Thursday its intention to join NATO with Sweden likely to follow soon after, diplomats and officials said, as Russia's invasion of Ukraine reshapes European security and the Atlantic military alliance.
NATO allies expect Finland and Sweden to be granted membership quickly, five diplomats and officials told Reuters, paving the way for increased troop presence in the Nordic region during the one-year ratification period.
In the wider Nordic region, Norway, Denmark and the three Baltic states are already NATO members, and the addition of Finland and Sweden would likely anger Moscow, which says NATO enlargement is a direct threat to its own security.
Russian President Vladimir Putin has cited the issue as a reason for his actions in Ukraine, which has also expressed a desire to eventually join the western alliance.
Moscow has repeatedly warned Finland and Sweden against joining NATO, threatening "serious military and political consequences".
Asked on Wednesday if Finland would provoke Russia by joining NATO, President Sauli Niinisto said Putin would be to blame. "My response would be that you caused this. Look at the mirror," Niinisto said.
On the frontlines, Ukraine on Wednesday said it had pushed back Russian forces in the east and shut gas flows on a route through Russian-held territory, raising the specter of an energy crisis in Europe.
Ukraine's armed forces' general staff said on Wednesday it had recaptured Pytomnyk, a village on the main highway north of the second-largest city of Kharkiv, about halfway to the Russian border.
The advance appears to be the fastest that Ukraine has mounted since it drove Russian troops away from the capital Kyiv and out of northern Ukraine at the beginning of April.
If sustained, it could let Ukrainian forces threaten supply lines for Russia's main attack force, and put rear logistics targets inside Russia within range of artillery.
But Russian forces were regrouping to prevent further advances, and had crossed the Donets River, where fighting was underway, the Ukraine general staff said on Thursday.
In Vilkhivka, another village near Kharkiv recaptured by Ukrainian forces in early April, resident Tatyana Pochivalova returned to find her home blasted to ruins.
"I have not expected anything like this, such aggression, such destruction," a weeping Pochivalova said. "I came and I kissed the ground, I simply kissed it. My home, there is nothing. Where am I to live, how am I to live?"
In the south, Ukraine's military said early on Thursday it had destroyed two tanks and an ammunition depot in the Russian-controlled Kherson region.
Viacheslav Chaus, governor of the northern Chernihiv region, said some civilians had been killed and wounded in the city of Novhorod-Siversky by Russian airstrikes on critical infrastructure, administrative buildings and private houses overnight.
Russia calls its actions in Ukraine a "special operation" to disarm Ukraine and protect it from fascists. It also denies targeting civilians.
Ukraine and the West say the fascist allegation is baseless and that the war is an unprovoked act of aggression, in which thousands of civilians have been killed and towns and cities destroyed.
Wednesday's move by Ukraine to cut off Russian gas supplies through territory held by Russian-backed separatists was the first time the conflict has directly disrupted shipments to Europe.
Gas flows from Russia's export monopoly Gazprom to Europe via Ukraine fell by a quarter after Kyiv said it was forced to halt all flows from one route, through the Sokhranovka transit point in southern Russia.
Ukraine accused Russian-backed separatists of siphoning supplies.
Should the supply cut persist, it would be the most direct impact so far on European energy markets.
Moscow has also imposed sanctions on the owner of the Polish part of the Yamal pipeline that carries Russian gas to Europe, as well as Gazprom's former German unit, whose subsidiaries service Europe's gas consumption.
The implications for Europe, which buys more than a third of its gas from Russia, were not immediately clear.
Burned out tanks
In southern Ukraine, where Russia has seized a swathe of territory, Kyiv has said Moscow plans to hold a fake referendum on independence or annexation to make its occupation permanent.
The Kremlin said on Wednesday it was up to residents living in the Russian-occupied Kherson region to decide whether they wanted to join Russia, but any such decision must have a clear legal basis.
Russian forces have also continued to bombard the Azovstal steelworks in the southern port of Mariupol, the last bastion of Ukrainian defenders in a city.
Ukraine says it is likely that tens of thousands of people have been killed in Mariupol. Ukrainian authorities say between 150,000 and 170,000 of the city's 400,000 residents are still living there amid the Russian-occupied ruins.
Video from Mariupol showed heavy equipment clearing rubble as residents charged mobile devices from a generator set up in a children's playground.
One resident, Sergei, described returning home to find a tank had blown up his apartment.
"I came home (from) the shelter, opened the door, but there was no apartment anymore. It was scary. Actually, it was very scary."