Russia was poised Wednesday to formally annex parts of Ukraine where occupied areas held a Kremlin-orchestrated "referendum" — denounced by Kyiv and the West as illegal and rigged — on living under Moscow's rule.

Armed troops had gone door-to-door with election officials to collect ballots in five days of voting. The results were widely ridiculed as implausible and characterized as a land grab by an increasingly cornered Russian leadership following embarrassing military losses in Ukraine.

Moscow-installed administrations in the four regions of southern and eastern Ukraine claimed Tuesday night that residents had voted to join Russia.

"Forcing people in these territories to fill out some papers at the barrel of a gun is yet another Russian crime in the course of its aggression against Ukraine," Ukraine's Foreign Ministry said, adding that the balloting was "a propaganda show" and "null and worthless."

European Commission President Ursula von der Leyen urged the European Union's 27 member countries to slap more sanctions on Russian officials and trade over the "sham referendums." She labeled the ballots "an illegal attempt to grab land and change international borders by force."

The ballot was "falsified" and the outcome "implausibly claimed" that residents had agreed to rule from Moscow, the Washington-based think tank Institute for the Study of War said.

Pro-Russia officials in Ukraine's Donetsk, Kherson, Luhansk and Zaporizhzhia regions said Wednesday they would ask Russian President Vladimir Putin to incorporate their provinces into Russia. Separatist leaders Leonid Pasechnik in Luhansk and Denis Pushilin in Donetsk said they were leaving for Moscow to settle the annexation formalities.

According to Russia-installed election officials, 93% of the ballots cast in the Zaporizhzhia region supported annexation, as did 87% in the Kherson region, 98% in the Luhansk region and 99% in Donetsk.

Western countries, however, dismissed the balloting as a meaningless pretense staged by Moscow in an attempt to legitimize its invasion of Ukraine launched on Feb. 24.

The U.S. ambassador to the United Nations, Linda Thomas-Greenfield, said Washington would propose a Security Council resolution to condemn the "sham" vote. The resolution would also urge member states not to recognize any altered status of Ukraine and demand that Russia withdraws its troops from its neighbor, she tweeted.

European Union foreign policy chief Josep Borrell called the vote "illegal" and described the results as "falsified."

"This is another violation of Ukraine's sovereignty (and) territorial integrity, (amid) systematic abuses of human rights," he tweeted.

Ukraine's Foreign Ministry statement asked the EU, NATO and the Group of Seven major industrial nations to "immediately and significantly" step up pressure on Russia with new sanctions and by significantly increasing their military aid to Kyiv.

The Kremlin remained unmoved amid the hail of criticism. Spokesman Dmitry Peskov said that at the very least, Russia intended to drive Ukrainian forces out of the Donetsk region, where Moscow's troops and separatist forces currently control about 60% of the territory.

Russia is calling up 300,000 reservists to fight in the war and warned it could resort to nuclear weapons after this month's counteroffensive by Ukraine dealt Moscow's forces heavy battlefield setbacks. The partial mobilization is deeply unpopular in some areas, however, triggering protests, scattered violence and Russians fleeing the country by the tens of thousands.

The mobilization prompted the U.S. Embassy in Moscow to warn Americans in Russia to leave immediately because "Russia may refuse to acknowledge dual nationals' U.S. citizenship, deny their access to U.S. consular assistance, prevent their departure from Russia, and conscript dual nationals for military service." Earlier embassy security alerts also advised Americans to leave, saying they could be harassed and have difficulty obtaining consular assistance.

The EU expressed outrage over the suspected sabotage Tuesday of two underwater natural gas pipelines from Russia to Germany and warned of retaliation for any attack on Europe's energy networks.

Borrell said "all available information indicates those leaks are the result of a deliberate act," even though the perpetrators haven't so far been identified.

"Any deliberate disruption of European energy infrastructure is utterly unacceptable and will be met with a robust and united response," Borrell said in a statement on behalf of the EU's 27 member countries.

Kremlin spokesman Peskov said allegations that Russia could be behind the incidents were "predictable and stupid," saying the damage has caused Russia huge economic losses.

The war has brought an energy standoff between the EU, many of whose members have for years relied heavily on Russian natural gas supplies, and Moscow.

The damage makes it unlikely the pipelines will be able to supply any gas to Europe this winter, according to analysts.

Ukraine's military and Western analysts said Russia is sending troops without any training to the front line.

In a briefing, the Ukraine military's general staff said the 1st Tank Regiment of the 2nd Motorized Rifle Division of Russia's 1st Tank Army has received untrained new troops.

The Ukrainian military also said prison convicts are reinforcing the Russian lines. It offered no evidence to support the claim, although Ukrainian security services have released audio of purportedly monitored Russian phone conversations on the issue.

The Institute for the Study of War cited an online video by a man who identified himself as a member of the 1st Tank Regiment, visibly upset, saying that he and his colleagues wouldn't receive training before shipping out to the Russian-occupied parts of the Kherson region.

"Mobilized men with a day or two of training are unlikely to meaningfully reinforce Russian positions affected by Ukrainian counteroffensives in the south and east," the institute said.

The U.K. Ministry of Defense said Ukraine's counteroffensive is advancing slowly, meeting a stouter Russian defense.

In the partially occupied Donetsk region Russian attacks killed five people and wounded 10 others over the last 24 hours, said Pavlo Kyrylenko, the head of the local military authority.

Authorities in the southern Ukrainian city of Nikopol said Russian rockets and artillery pounded the city overnight.

The city, across the Dnieper River from Russian-occupied territory, saw 10 high-rises and private buildings hit, as well as a school, power lines and other areas, said Valentyn Reznichenko, the head of the local military administration.