The school shooting has been dubbed the 'Russian Columbine'
Crimea mourns victims of school massacre
Crimea on Friday was to hold a memorial ceremony for the 20 people killed in a school shooting dubbed the "Russian Columbine", the worst massacre of its kind in the country's history.
On Wednesday, 18-year-old Vladislav Roslyakov opened fire on his technical college in the city of Kerch before killing himself. More than 40 others were injured in the attack.
The ceremony, attended by authorities from the Moscow-annexed peninsula, will begin in the morning in the centre of Kerch.
Security has been stepped up in the city of 150,000, which sits in the far east of Crimea and is where a recently-opened bridge links the Russian mainland to its new territory.
All central roads have been closed.
Residents have been laying flowers at the central square.
The mourning ceremony will be followed by a procession towards Kerch's new cemetery.
Of those injured in the attack, a number remained in a "very serious condition", according to Russian health minister Veronika Skvortsova.
Many of those hospitalised were injured by an explosion that blasted metal ball bearings and other items into their bodies.
Six have been transferred to the Russian capital for further treatment, Moscow mayor Sergei Sobyanin said.
On Thursday, a girl claiming to be Roslyakov's ex-girlfriend told Russian media he had spoken of taking revenge for bullying.
"He would say that he lost trust in people when his classmates began humiliating him for not being like everyone else," a 15-year-old named as Zlata told the Kremlin-funded RT television outlet.
"Vladislav was always telling me about his frequent fights with people around him," she said, adding that he "didn't want to live" because of it.
President Putin meanwhile said the killing was the "result of globalisation" and the continuation of a trend that had begun in the US.
Several media outlets made a comparison with the 1999 Columbine High School shooting in the US, which left 13 people dead.
They described photographs circulating on the internet showing Roslyakov wearing a similar T-shirt to Eric Harris, one of the Columbine killers.
Investigators are working to establish the teenager's exact motive and whether he was working alone.
According to the Russian Kommersant newspaper, the teenager "grew up in a rather poor family" with a disabled father. The paper said Roslyakov's mother is a Jehovah's Witness - a Christian organisation considered "extremist" and banned in Russia.
Russian television reported she works as an orderly at one of the hospitals that treated victims.
According to the RIA Novosti agency, security forces raided Roslyakov's family home following the killings.