AMNA NAWAZ: Today, Moscow woke to a dramatic image, an apparent drone exploding over the Kremlin, the heart of Russian power.

The Russian president's press service accused Ukraine of a failed assassination attempt.

But Kyiv denies any involvement.

Nick Schifrin is following today's developments, joins me here now.

Nick, good to see you.

NICK SCHIFRIN: Thank you very much.

AMNA NAWAZ: You have been reporting on this all day.

What do we know at this hour about what happened?

NICK SCHIFRIN: Moscow says that two drones flew over the Kremlin after about 2:00 in the morning.

And cameras filmed two explosions about 15 minutes apart.

You see there the drone highlighted there and the explosion there, about 15 minutes apart, two explosions.

And analysts say -- that's it slowed down right there.

And analysts say what we're watching is a small drone probably unarmed exploded or brought down by Russian air defense.

Now, as you said the Kremlin called that a failed assassination attempt against Russian President Vladimir Putin, even though Putin was not in the Kremlin at the time.

But Ukrainian President Volodymyr Zelenskyy, visiting Finland, denied any involvement.

VOLODYMYR ZELENSKYY, Ukrainian President: We don't attack Putin or Moscow.

We fight on our territory.

We are defending our villages and cities.

We don't have, you know, enough weapon for this.

And we didn't attack Putin.

We leave it to tribunal.

NICK SCHIFRIN: Tribunal, a reference to Russian war crimes there.

U.S. officials I talk to say they're working on what they think actually happened.

But one U.S. official said, regardless of the origin of the explosion, the U.S. was not given any warning.

But we did hear U.S. skepticism of Russia's claims today from Secretary of State Antony Blinken talking to The Washington Post's David Ignatius.

ANTONY BLINKEN, U.S. Secretary of State: Well, first, I have seen the reports.

I can't in any way validate them.

We simply -- we simply don't know.

Second, I would take anything coming out of the Kremlin with a very large shaker of salt.

NICK SCHIFRIN: A shaker of salt, U.S. denying - - or have some skepticism of Russian.

Sorry.

But what we heard from Russian pro-war bloggers today is that this was not going to change the war.

And that seemed to indicate this wasn't any kind of dramatic assassination attempt or could preclude to any escalation.

AMNA NAWAZ: So that's really dramatic video.

It's been making the rounds and everyone's been examining it, talking to sources.

You have been talking to every analysts and experts you have in your contact list.

What do they believe happened?

Is there consensus?

NICK SCHIFRIN: There's definitely not consensus.

Some believe that this could have been a Russian false flag operation, meaning the Kremlin launched the drone itself, brought the drone down itself, in order to preclude some kind of future escalation in Ukraine, or to add to the narrative that Putin has been saying, that it is Ukraine that is attacking Russia.

But others say that's unlikely, one, because this actually revealed the vulnerability of Russia's air defense, the fact that the drone actually got over the Kremlin... AMNA NAWAZ: Right.

NICK SCHIFRIN: ... and was not exploded until it was actually inside the Kremlin complex.

And they point out that there were multiple drone crashes in recent days around Moscow, likely by either independent people acting on Ukraine's behalf or by Ukraine itself.

Ukraine does have drones that fit this description, both Ukrainian-made and Chinese-made.

And Samuel Bendett, a Russian studies analyst at the think tank CNA, says that this could have been Kyiv sending a signal.

SAMUEL BENDETT, Center for Naval Analyses: If it was a Ukrainian drone strike, it demonstrated to the Russian military and the Russian government that Ukraine can strike into the very heart of Russia.

This may have been a symbolic attack sent to demonstrate that, next time, or the time after that, a Ukrainian drone can carry a lot more bombs, a lot more munitions, could be a lot more precise.

NICK SCHIFRIN: But, again, Kyiv denies any involvement.

The U.S. reiterated today it neither encourages nor enables Ukraine to attack inside Russia.

But what Kyiv does not deny, including to me last week by Ukraine's military intelligence chief, is the idea that it uses Ukrainian weapons to attack inside Russia.

In recent days, we have seen an uptick of those attacks, derailment of trains along Russia's supply lines into Ukraine.

And we have also seen an explosion of a fuel storage depot near the border right there with Russia.

U.S. officials call these shaping operations to degrade Russian supply lines, Amna, ahead of Ukraine's expected counteroffensive.

AMNA NAWAZ: Meanwhile, Nick, on a related front, we now have had some comments from Ukrainian President Zelenskyy commenting on those recent U.S. intelligence leaks, right, especially the ones that revealed some Ukrainian military information.

And what did he have to say?

NICK SCHIFRIN: Yes, we spoke to two Ukrainian senior officials in the last few weeks about documents that really detailed a lot of information about Ukraine's military, and they both downplayed the documents and suggest that they had no impact on Ukraine or the bilateral relationship.

Zelenskyy did not downplay their impact.

He gave an interview to The Washington Post's Isabelle Khurshudyan.

And he was very critical.

He said he did not receive any information beforehand and said -- quote -- "It is unprofitable for us.

It is not beneficial to the reputation of the White House, and I believe it is not beneficial to the reputation of the United States."

The documents revealed Ukrainian air defense shortages.

They revealed details of the units that are about to launch this counteroffensive against Russia.

They also reveal the U.S. told Kyiv not to attack Moscow on the one-year anniversary of the full-scale invasion.

And they revealed that the U.S. spies on Zelenskyy and his senior staff.

And asked if he was angry about U.S. spying, he said or he indicated that airing his private feelings were not worth the potential diplomatic harm.

Now, Secretary of State Antony Blinken, the Defense Department, the Joint Chiefs of Staff, they all reached out to their counterparts as the leaks hit the news.

And, frankly, both sides were quite surprised, U.S. officials taken aback and caught off guard, just as Ukraine was.

AMNA NAWAZ: Ripple effects of that leak still being felt.

Nick Schifrin, thank you for your reporting.

NICK SCHIFRIN: Thank you.