Ilnaz Galyaviev appeared in court dressed in black, accused of opening fire at School 175 in the city of Kazan in an attack that killed seven children and two adults and wounded many more.

He behaved calmly and confidently and told the court he had no serious illnesses. He did not give a plea in Wednesday's hearing.

A court ordered Galyaviev to be held in custody for two months pending trial. State investigators said he had fired at least 17 rounds and detonated an explosive device in the attack in the city 725 kilometres east of Moscow.

The Investigative Committee, which handles probes into serious crimes, said Galyaviev's relatives had noticed him behaving aggressively and having a short temper this year.

In a statement, it said he had repeatedly sought medical treatment for severe headaches and he was also diagnosed with a brain disease last year.

The deadliest school shooting since 2018 when a student at a college in Russian-annexed Crimea killed 20 people has stunned the city of Kazan.

Mourners brought toys and flowers to the school in tribute from the early hours on Wednesday.

The head of Russia's Muslim-majority region of Tatarstan, where Kazan is the main city, has called it a national tragedy and the Kremlin has called for tighter gun controls.

Russia has strict restrictions on civilian firearm ownership, but some categories of gun are available for purchase for hunting, self-defence or sport, subject to tests and other requirements.

About 100 people gathered at a traditional Muslim funeral for Elvira Ignatieva, an English teacher who was among the victims.

"She was protecting her children ... She was protecting (them) and didn't hide away," said Talgat Gumerov, a Kazan resident.

Twenty-three people were still in hospital on Wednesday, including 12 children with gunshot wounds, the TASS news agency reported.

Five children were in a serious condition and one of them was critical, it said.

Australian Associated Press