President Vladimir Putin declared two days of national mourning from Monday. All flags are to fly at half mast over government buildings and entertainment programmes will be pulled off the air, the Kremlin said.
In the grief-stricken town of Beslan, the grim task of burying the victims was set to continue.
Dozens of well-wishers on Sunday laid red carnations and plastic bottles of water at the wreckage of School Number One, its charred remains a haunting memory to a three-day standoff that ended with a massacre in some of the most violent scenes in recent Russian history.
The water bottles were a stark symbol of how the children were left without water or food by their captors, who demanded independence for separatist Chechnya.
Meanwhile, deputy prosecutor General Sergei Fridinsky said in comments broadcast by Russia's Channel One television that the first alleged hostage-taker was due to be charged late on Sunday.
"This man personally took part in the attack, he was part of that gang, he took part in shooting. Today he will be charged," said Fridinsky. "They will all be punished for all the crimes they committed, and this man among others."
"By Allah, I have not shot... By Allah, I have not killed"
The suspect, whose name and nationality were not released, was shown with his hands handcuffed behind his back, insisting in strongly accented Russian that "By Allah, I have not shot" and "By Allah, I have not killed".
On Sunday, up to 22 victims of the siege were buried.
Casualty figures continued to swing wildly, with the official death toll from Friday's carnage standing at 335 people although a worker in the region's main morgue said that it had already received 394 bodies.
Some 377 people, including 197 children under 17, remained under local medical care, 55 of them in severe condition, North Ossetia's Deputy Health Minister Teymuraz Revazov was quoted by the Interfax news agency as saying.
Another 27 children who were rushed to hospitals in Moscow and Rostov-on-Don over the weekend also remain in severe condition, the ITAR-TASS news agency reported.