VIENNA - A three-day national mourning began on Tuesday in Austria after the country was "stricken at the heart" by a mass school shooting earlier in the morning.

At least 11 people were killed, including the shooter, in the school shooting that happened in Austria's second-largest city of Graz, according to local media reports. Another 11 were hospitalized with serious injuries.

The school shooting is considered one of the most serious shootings in the history of Austria, the country's largest newspaper Kronen Zeitung said.

Austrian President Alexander Van der Bellen on Tuesday announced a three-day national mourning and the lowering of the country's flag to half-staff, saying that "what happened today in a school in Graz strikes our country at the heart".

Government leaders, including Austrian Chancellor Christian Stocker, Vice-Chancellor Andreas Babler and Foreign Minister Beate Meinl-Reisinger, gathered in Graz on Tuesday evening at an event in memory of the victims.

"Schools are symbols of youth, hope, and the future. It's hard to bear when schools become places of death and violence," said European Commission President Ursula von der Leyen on the social platform X.

According to the Kronen Zeitung, the shooting occurred at the school of BORG in Dreierschutzengasse in the Lend district shortly before 10 am local time (0800 GMT) on Tuesday. Police confirmed the suspected perpetrator as a 21-year-old shooter, who used to be a student at BORG. He is reported to have shot himself dead.

Police have been mobilized in the region, with a helicopter deployed. The school has been evacuated, and further danger is excluded, local police stated on X.

On Wednesday morning, a nationwide minute of silence will be observed at 10 am local time. Public celebrations have been canceled or postponed.

"You don't have words for such things. Austria is such a lovely country. We stay together, we live together, and such tragedies like this today is unbelievable," a resident of Graz said.