At least two people were killed as Russia pounded energy facilities across Ukraine with dozens of missiles on Friday.

The attack knocked out electricity in some areas and forced Kyiv to introduce emergency power cuts across the entire country.

The latest in a series of big waves of missile strikes since October hammered critical infrastructure and drove people into shelters as residential areas also came under fire.

The mayor of Ukraine's second city, Kharkiv, reported "colossal" damage, leaving many people without heating in freezing winter temperatures.

Russia fired more than 60 missiles during the morning rush hour and tried to distract Ukrainian air defenses by flying warplanes near Ukraine, Air Force spokesperson Yuriy Ihnat said.

"They want to destroy us, and make us slaves. But we will not surrender. We will endure," said Lidiya Vasilieva, 53, as she headed for shelter at a Kyiv railway station. "I want the war over and soon. But I am ready to wait as long as needed."

Two people were killed in the central city of Kryvyi Rih, and a third died in a fire in the southern Kherson region after an apartment block was hit by shelling, authorities said.

The attack in Kryvyi Rih, President Volodymyr Zelenskyy's hometown, also wounded at least eight people, including three small children, and a rescue effort was still underway, a senior official said.

The central city of Poltava and parts of Kyiv were among areas where power was knocked out. Critical infrastructure was hit in the northeastern region of Kharkiv, the Black Sea region of Odessa and in Vinnytsia in west-central Ukraine.

Three loud blasts could be heard in Kyiv and smoke wafted towards a part of the city, Reuters witnesses said. The railway operator said a number of railway lines were left without power.

"There is colossal damage to infrastructure, primarily the energy system," Kharkiv Mayor Ihor Terekhov said. "I ask you to be patient with what is happening now. I know that in your houses there is no light, no heating, no water supply."

Kyrylo Tymoshenko, deputy head of Zelenskyy's office, said emergency power shutdowns had been introduced nationwide to enable repairs after damage to energy facilities in several regions which he did not identify.

Ukraine Defiant

The initial air alert in Kyiv was lifted four hours after it was announced as children made their way to school and people traveled to work.

The cavernous Kyiv metro system, which has one of the deepest stations in the world, stopped functioning and was used as a bomb shelter.

Russia, which invaded Ukraine in February, Moscow says attacks on basic infrastructure are militarily legitimate. Ukraine says attacks intended to cause civilian misery are a war crime.

"The goal of the Russian Federation is for Ukrainians to be constantly under pressure, to go down into bomb shelters almost every day, to feel discomfort due to power outages or water interruptions," Economy Minister Yulia Svyrydenko wrote on Facebook.

"But Ukraine's position is unchanged: let it be without light, but #withoutyou. We will endure. We will win. We will rebuild."