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.

Russia's FSB intelligence agency said on Thursday it had detained a journalist working for The Wall Street Journal on spying charges.

Russian state media cited an FSB statement saying Evan Gershkovich was detained in Ekaterinburg, a city in central Russia, and accusing him of collecting "state secrets" on an enterprise belonging to Russia's military industrial complex on behalf of the United States.

A criminal case has been opened against him, the officials said.

"It is established that Evan Gershkovich, acting on the instruction of the American side, was collecting information consisting of state secrets, about the activity of one of the enterprises of the Russian military industrial complex. He was arrested in Ekaterinburg during an attempt to receive secret information," Russian media said, quoting FSB officials.

Earlier reports from local media said that Gershkovich had been in Ekaterinburg reporting on the Wagner private military company.

Gershkovich is a reporter for the WSJ covering Russia, Ukraine and the former Soviet Union. He previously reported for Agence France-Presse and The Moscow Times, according to his WSJ profile. He also served as a news assistant at The New York Times.

-ABC News Tanya Stukalova and Patrick Reevell