Situation outside secondary school No.88 where a gunman opened fire killing 6 people and wounding 20, and killed himself. Photo: VCG

At least 13 people were killed, including seven children, in a shooting at a school in the Russian city of Izhevsk on Monday, TASS news agency reported, citing the Russian Investigative Committee.

According to the committee, 14 children and seven adults were injured in the attack at the No.88 school located near the city administration building of Izhevsk, the capital city of western Russia's Udmurt Republic.

It was reported earlier that nine people were killed and about 20 others wounded in the shooting.

The shooter has committed suicide and his body has been found, the committee said, adding that he was wearing a black T-shirt with Nazi symbols and a balaclava.

He was later identified as a local man born in 1988, who graduated from this school.

The governor of the Udmurt Republic declared three days of mourning beginning on Monday.

Russian President Vladimir Putin denounced the "inhuman terrorist attack," the Kremlin said, adding that the shooter "apparently belongs to a neo-fascist group." 

Russia's last major school shooting was in April, when an armed man opened fire in a kindergarten in the central Ulyanovsk region, leaving a teacher and two children dead.

The shooter, described as "mentally ill," was later found dead, with officials saying he had shot himself.