A deadly blast that ripped through a college in Russia-annexed Crimea on Wednesday is being investigated as a possible terror attack, the Kremlin said.
State news agencies quoted the Russian National Counterterrorism Committee (NAK) as saying it was caused by an unidentified explosive device.
Around 20 people have been rushed to hospital by paramedics and doctors are expected around 50 more wounded.
Eyewitnesses at the school, attended by children between the ages of 14 and 18, said gunmen fired into the air before the explosion, Russian media reported.
Reuters news agency said the schools and pre-schools were being evacuated in the city after the blast.
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The royal couple were scheduled to spend their day in Dubbo, also visiting a drought-stricken farm and a local school. Their first official engagement in Dubbo was at the dedication of a new plane for the Royal Flying Doctor Service.
"The majority of them are teenagers", the committee said in a statement, adding that the metallic device was planted in the school's cafeteria.
Crimea, officially part of Ukraine, was seized by Russian Federation in 2014 and annexed after a disputed vote that was widely condemned by the worldwide community. Putin offered his condolences to the families of the victims.
Crimean authorities said initial information suggests the blast was caused by a "gas canister" that "blew up" inside the college's canteen.
Russia's National Guard has called the explosion an act of terrorism, while the investigative committee has opened a terrorism probe.
Crimean Prime Minister Sergei Aksyonov and Russia's health minister were en route to the scene. Kerch is the point on the peninsula where a bridge linking Crimea to Russian Federation makes landfall on the Crimean side.Putin opened the bridge to road traffic in May this year, getting behind the wheel of a truck to drive it across the bridge.