What We Know About the Explosions Over the Kremlin

A day after the Kremlin accused Ukraine of deploying two drones to kill President Vladimir V. Putin, deep questions remain about the episode that heightened tensions ahead of Ukraine’s expected counterattack.

Ukrainian President Volodymyr Zelensky has vehemently denied any involvement in the attack on the Kremlin, which would have been a terrifying assault on the fortress-like complex in the heart of the Russian capital. He accused Moscow of planning the explosion to drum up public support before “a large-scale terrorist provocation.”

Here’s what we know about the episode and its aftermath.

What’s up?

Video verified by The New York Times showed two explosions 15 minutes apart above the Kremlin, just before 2:30 a.m. on Wednesday. The explosion appears to have been caused by a drone.

One explosion caused a brief fire, although it is unclear whether the drone exploded as planned or was shot down. It cannot be determined from where they will be launched.

About 12 hours after the explosion, the Kremlin issued a rare statement saying it had failed in an “attempt on the president’s life,” which the Kremlin did not have at the time. The Kremlin houses the Russian Senate and the apartment where Mr. Putin occasionally lives, among other offices.

There were no casualties or serious damage, the Kremlin said.

What are Russia and Ukraine talking about?

Both have blamed the other for the explosion.

In a lengthy statement, Russia’s Defense Ministry announced on Wednesday that it reserves the right to take “retaliatory measures where and when appropriate.” The statement did not include any evidence of Ukrainian involvement.

Ukrainian government and military intelligence officials, who have traditionally followed a policy of deliberate ambiguity about attacks on Russian territory, immediately said they had no role in any attack on the Kremlin. He accused Russia of creating the incident to justify escalating attacks in Ukraine or to bolster public support for the war.

Dmitri S. Peskov, Mr. Putin’s spokesman, claimed without evidence on Thursday that the United States was responsible for “dictating” Ukraine’s attack on Russia. John F. Kirby, a White House spokesman, immediately denied the allegations, saying of the incident: “Whatever it is, it’s not something we’re involved in.”

Russia’s claims have left U.S. intelligence officials fumbling with thin facts to determine what happened and why Moscow may be risking embarrassment by paying so much attention to another security failure amid the highly publicized military struggle in Ukraine.

“We just don’t know,” Secretary of State Antony J. Blinken said on Wednesday, adding: “I’ll take anything that comes out of the Kremlin with a very large shaker of salt.”

What could happen next?

The incident could become a pretext for Mr. Putin to escalate the war, perhaps by attacking government buildings in Kyiv or trying again to undermine the Ukrainian government.

Kremlin officials have repeatedly hinted at the possibility of using nuclear weapons, and war hawks have pushed for other plans to increase troop numbers.

On Thursday, Ukrainian air defenses shot down Russian drones and missiles fired at Kyiv and Odesa, the latest in a series of attacks on cities and towns in recent days. In Odesa, the Ukrainian military released images showing that some of the drones had handwritten messages that read “To Moscow” and “To the Kremlin.”

Tensions are particularly high as Kyiv prepares a counteroffensive to retake territory in eastern and southern Ukraine held by Russia. Ukrainian forces are preparing tens of thousands of soldiers and stepping up attacks on Russian targets, including in occupied Crimea. And on Tuesday, Russia will commemorate Victory Day, a major holiday marking the Soviet victory in World War II.

Even with the brutality of the full-scale invasion of Ukraine, Moscow has threatened violence in response to a major attack on Russian-held territory. Last fall after explosions destroyed a major bridge between Russia and Crimea, Moscow began a campaign of airstrikes against Ukraine’s civilian infrastructure that cut heat and electricity to millions of Ukrainians as temperatures plummeted.