But the ballots were widely discredited and earned the Kremlin no relief on Wednesday from international pressure over its assault on its neighbour.

Pro-Moscow administrations of all four occupied regions of southern and eastern Ukraine said on Tuesday night that their residents voted to join Russia in five days of Kremlin-orchestrated balloting.

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

Russian-installed officials in those occupied regions said they would ask President Vladimir Putin to incorporate them into Russia.

Western countries, however, dismissed the ballots as a meaningless pretence staged by Moscow in an attempt to legitimise its invasion of Ukraine.

The US ambassador to the United Nations, Linda Thomas-Greenfield, said Washington would propose a UN Security Council resolution to condemn Russia's "sham" vote.

The resolution would also urge member states not to recognise any altered status of Ukraine and demand that Russia withdraws its troops from its neighbour, she tweeted.

The European Union's foreign policy chief, Josep Borrell, also weighed in on the ballots, on Wednesday calling them "illegal" and describing the results as "falsified."

In Kyiv, Ukraine's foreign ministry blasted the ballots as "a propaganda show" and "null and worthless."

"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," a foreign ministry statement said.

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

The EU also expressed outrage over the suspected sabotage on 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.

Peskov, the Kremlin spokesman, said allegations that Russia could be behind the incidents were "predictable and stupid." He told reporters in a conference call that the damage has caused Russia huge economic losses.

The war in Ukraine 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.

In the eastern Ukrainian region of Donetsk, which is partially occupied by Moscow, Russian fire 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 Dnipro 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.

Australian Associated Press