Putin vowed to punish those behind concert massacre.
Ukrainian presidential adviser Mykhailo Podolyak said on Friday that Kyiv had nothing to do with Friday's attack by gunmen at a Moscow concert hall.
The United States had warned Russia on March 8 that "extremists" had imminent plans for an attack in Moscow.
The student is currently serving a 10 day sentence.
The embassy, which has repeatedly urged all US citizens to leave Russia immediately, gave no further details about the nature of the threat.
Russia's FSB said that the members of the organization had been planning "to commit a terrorist act against one of the Jewish religious institutions in Moscow."
Russia’s role as the host and mediator of these talks is particularly noteworthy. Moscow appears to be leveraging its perceived victories in Ukraine to expand its influence in the Middle East.
"We want to show our readiness... to engage and to be ready, just to not to be seen as an obstacle between the implementation of any process that should take further," he said.
The edition ran with a front-page photograph of a smiling Navalny with the caption: "...but there is hope!"
The event provoked a powerful backlash at a time when Russia is waging war in Ukraine and authorities are promoting an increasingly conservative social agenda.