Responding to Russia's accusation that the U.S. was behind Wednesday's drone attack on the Kremlin, White House spokesperson John Kirby said it was a "ludicrous claim."

"There's a word that comes to mind that I'm obviously not -- not appropriate to using on national TV," Kirby said on CNN on Thursday.

"I will just tell you Mr. Peskov is lying, and I mean, that's obviously, it's a ludicrous claim," he added. "The United States had nothing to do with this. We don't even know exactly what happened here, Kaitlin. But I can assure you, the United States had no role in it whatsoever."

Kirby said the U.S. does not have any information on who is behind the strike but are "trying to learn more about this as best we can."

-ABC News' Justin Gomez

Russian President Vladimir Putin's spokesman accused the United States of being involved in the drone attack on the Kremlin on Wednesday.

"We understand well that the decision about such terror attacks are taken not in Kyiv, but in Washington," Dmitry Peskov told reporters in a briefing. "Often targets are determined not in Kyiv but in Washington. They don't Kyiv the right everytime in choosing the means. In Washington they also clearly understand that we know that."

He added, "Without question. Such decisions -- the determining of targets and means -- are all dictated to Kyiv from Washington."

Peskov said it was important that Washington understand the "danger" of such involvement in an attack.

-ABC News' Patrick Reevell

Russian forces launched a "complex air strike" with "drones and missiles" on Kyiv early Thursday morning, the Kyiv City Military Administration said on Telegram.

The air raid siren went off in Kyiv for three and a half hours during the attack, the Kyiv City Military Administration said.

There were no casualties or injuries from the strikes.

"According to preliminary information, all the missiles and UAVs were destroyed," the Kyiv City Military Administration added.

This was the third attack on the capitol in four days, the administration said.

-ABC News' Natalia Kushniir

The U.S. Embassy in Ukraine sent an alert to Americans on Wednesday warning of an "ongoing heightened threat of missile attacks," including in Kyiv.

"In light of the recent uptick in strikes across Ukraine and inflammatory rhetoric from Moscow, the Department of State cautions U.S. citizens of an ongoing heightened threat of missile attacks, including in Kyiv and Kyiv Oblast," the alert stated.

The U.S. Embassy urged U.S. citizens to follow guidance from local authorities and to observe air alarms and shelter appropriately.

Chinese President Xi Jinping hadn't even left Moscow when the drones started exploding. It came a matter of hours after Xi and Russian President Vladimir Putin proclaimed they were the ones who wanted to make "peace" in Ukraine.

Ukrainian officials say 21 lethal attack drones were launched overnight and into this morning by Russia, with 16 shot down by the Ukrainians.

An apartment block was hit in a town southeast of Kyiv, killing at least four people and injuring others, officials said. Russian officials claim Ukrainian soldiers were based there. The Ukrainians are calling it a "civilian" building.

Russian missiles later hit an apartment block in the heart of the southern Ukrainian city of Zaporizhzhia.

And in an apparent repost to the geopolitical theatrics in Moscow, Ukrainian President Volodymyr Zelenskyy visited his troops on Wednesday in the eastern Donbas, not far from the embattled city of Bakhmut, according to his officials.

Bakhmut has become a potent symbol of Ukrainian resistance and sacrifice and despite being surrounded on three sides Ukrainian forces inside the city are, after months of fighting there, still holding on.

Zelenskyy's office released video of him addressing troops and also visiting injured soldiers in a military medical facility in the region. He told troops their "destiny was difficult but important" because they were fighting to save the motherland.

-ABC News' Tom Soufi-Burridge and Yulia Drozd