Russia-Ukraine updates: Putin says war was ‘unleashed’ on Russia

The investigation into who was behind the Nord Stream natural gas pipeline explosion should be "objective, impartial and transparent," Russian Foreign Minister Sergei Lavrov told Russian news agency Interfax.

"I do not want to threaten anyone. I do not want to hint at anything either. I just know that this flagrant terror attack will not go uninvestigated," Lavrov added.

Russia also said it will distribute its correspondence with Germany, Denmark and Sweden on the investigation of the Nord Stream explosion among the members of the United Nations Security Council soon.

Russia claimed the three countries are denying Russia access to information and participation in the investigation, first deputy permanent representative to the U.N. Dmitry Polyansky said in an interview, according to Russian news agency TASS.

-ABC News' Anastasia Bagaeva and Tanya Stukalova

Ukrainian President Volodymyr Zelenskyy denied that Ukraine had anything to do with the Nord Stream gas pipeline explosions last year.

"As for the Nord Stream, we have nothing to do with it," Zelenskyy said Friday.

The New York Times published a report that U.S. intelligence suggests that a pro-Ukrainian group sabotaged the pipeline.

Zelenskyy also suggested that the information being spread about the involvement of pro-Ukrainian groups in the attack could be done to slow down aid to his country.

-ABC News' Natalia Shumskaia

Electricity supply has been fully restored in Kyiv after Russia's overnight barrage of missile attacks on Ukraine, Kyiv Mayor Vitaliy Klitschko said in a Telegram post Thursday.

Also, the Zaporizhzhia nuclear power plant is now "receiving electricity for its own needs from the Ukrainian grid after power supply was cut," Russian news agency Interfax reported.

-ABC News' Tatiana Rymarenko and Natalia Shumskaia

Russia's overnight barrage of missiles aimed at civilian infrastructure may have knocked heat out to as much as 40% of Ukrainians, the White House said on Thursday.

Russian President Vladimir Putin is attempting to "brutalize" the people of Ukraine, John Kirby, spokesperson for the White House National Security Council, told ABC News' George Stephanopoulos on "Good Morning America" on Thursday.

"It also appears, George, that they were definitely targeting civilian infrastructure," Kirby said. "I would agree with the Ukrainians. He's just trying to brutalize the Ukrainian people"

Russian forces early on Thursday launched 81 missiles from land and sea, Ukrainian officials said. Eight uncrewed drones were also launched in what officials described as a "massive" attack.

Eleven regions and cities were targeted in an attack that lasted at least seven hours, officials said.

Kirby said on Thursday that the White House expects to see more fighting on the ground in Ukraine for at least the "next four to six months."

"We know that the Russians are attempting to conduct more offensive operations here when the weather gets better," he said.