This was not too long ago, and since it comes from Putin’s mouth it can be taken to be authoritative:
Megatron @Megatron_ron
BREAKING:
 Putin in a speech right now:
“All the perpetrators of the terrorist attacks have been found and detained. They tried to hide on the territory of Ukraine. A window was prepared at the border to enter the territory of Ukraine.”
http://t.me/megatron_ron
[video]
He also stated:
“A just and inevitable punishment awaits those who direct them [terrorist acts], whoever they are. To reiterate, we will identify and punish everyone who stands behind the terrorists who prepared this atrocity, this attack on Russia, on our people.”
The reported fact that “a window” for escape into Ukraine had been prepared for the perps obviously establishes a strong presumption of Ukrainian—and possibly Western—complicity. In particular, the fact that MI6—and possibly CIA—trained Ukrainians in sabotage and assassination, specifically with regard to operating within Russia, a presumption of some degree of responsibility on the part of the Anglosphere Deep State. Certainly that is almost certainly a working presumption on the part of the Russian leadership. Notably, in April last year Dmitry Medvedev—widely regarded as bad cop to Putin’s good cop—wrote:
"Britain was, is and will be our eternal enemy.”
Was this one of the “nasty surprises” that Nuland claimed—shortly before “retiring”—awaited Russia?
Yesterday we pointed out that the US, UK, and Israel are known to support terrorist groups in Syria.
Here’s some reporting on that angle (second tweet below). I’m agnostic at this point since, in any event, the directors behind the attack are certainly Western/Ukrainian:
Megatron @Megatron_ron
The terrorists were caught only 150 km before they managed to escape to Ukraine
7:23 AM · Mar 23, 2024
Note the reference in this next tweet to US financing for Syrian based terrorists:
Megatron @Megatron_ron
BREAKING:
 Terrorists from Moscow fled to Ukraine to the leader of Syrian terrorists
The photo shows Abdulhakim Shishani, one of the leaders of the Idlib radicals (Israel-US backed rebels in Syria), in whose group bandits escaped from the CIS.
And the photo of the international commander of the militants was taken in the border zone near the Belgorod region, during the attack that happened a few days ago.
Sishani has been in Ukraine for a long time, not in Syria. And he is the link between the Main Intelligence Directorate of the Ukrainian Ministry of Defense and the radical militants he commanded in Syria.
It is even more interesting that this "satanic" gang was financed by the USA and Britain, along with the so-called "moderate" groups.
Attempts to pretend that Ukraine had nothing to do with the terrorist attack in Crocus City Hall look very pale.
Against the background of the fact that the perpetrators of the terrorist attack were trying to escape to Ukraine to their patrons.
http://t.me/megatron_ron
6:55 AM · Mar 23, 2024
From RT's editor-in-chief Margarita Simonyan
"We already know the names of the perpetrators. We have seen their faces and know what they are saying during interrogations. (We are not publishing to avoid disrupting the investigation.)
And immediately it becomes clear why yesterday American media were shouting in unison that it was ISIS.
Because it's not ISIS. The perpetrators are simply chosen to convince the gullible global public that it is ISIS.
It's a simple sleight of hand. The level of a street corner shell game.
So here's the thing. It's not ISIS at all. It's Ukrainians. And the fact that even before the arrests, before the perpetrators' faces and names were known, Western intelligence agencies began to persuade the population that it was ISIS—that's what ignited the fire under this thief's hat.
It's not ISIS.
It's a well-coordinated team from several other, also widely known, abbreviations."
“Other widely known abbreviations” seems a broad hint that the coordination for the attack was directed by intel agencies—Ukrainian, but also possibly agencies with better known acronyms, such as: CIA and MI6.
Readers may well have seen some of the “preliminary interrogations” of the captured perps that are already circulating on the internet. No doubt the FSB has ways of getting them to talk. And no doubt there will be a lot more coming out over the course of today and following days.
It certainly was ISIS
The Israeli Secret Intelligence Service
Nuland is a monster.