The death toll from the Izhvesk school shooting has risen to 17, including 11 children, Russia's Investigative Committee said on Monday.

Another 24 people were injured, according to the committee.

A group of specialists has been sent to Izhevsk to provide medical assistance, the health ministry said.

An unidentified gunman opened fire at a school in Izhevsk, killing a security guard and many others before committing suicide, RIA news agency reported earlier, citing Governor Alexander Brechalov of the Udmurtia region, of which Izhevsk is the capital.

The motive for the shooting was unclear.

The Investigative Committee, which handles major crimes, said the gunman was wearing a balaclava and a black T-shirt with Nazi symbols. It said his identity had not yet been established.

UN Secretary-General Antonio Guterres on Monday condemned the fatal school shooting in Russia, said his deputy spokesman Farhan Haq.

"He strongly condemns this act of violence and expresses his deepest condolences to the families of the victims, as well as to the government and people of the Russian Federation. He wishes those injured a speedy and full recovery," Haq said in a statement.

Russian President Vladimir Putin denounced the tragedy as an "inhuman terrorist attack," the Kremlin said.  

"President Putin deeply mourns the deaths of people, children at a school where there was a terrorist attack by a person, who apparently belongs to a neo-fascist group," Kremlin spokesman Dmitry Peskov told reporters.

(With input from agencies)