At least eight students and a security guard are dead after a shooting at a school in Serbia's capital, Belgrade.

Another six pupils and a teacher were injured in the attack and have been taken to hospital, the interior ministry said in a statement.

Police arrested a 13-year-old student at the Vladislav Ribnikar primary school in central Belgrade over Wednesday morning's attack.

It is the first shooting of its kind in Serbia, the education minister said.

Officers in helmets and bulletproof vests cordoned off the area around the school, located in the central Vracar neighbourhood, shortly after 08:40 (06:40 GMT).

Officials told reporters at a news conference in Belgrade that the suspect had called police himself after the attack.

An investigation into the motives behind the incident is under way.

The suspect, whom the police have named as Kosta Kecmanovi?, is alleged to have used his father's guns, both of which had legal permits.

The boy's father has since been arrested and Serbia's interior minister said "legal measures" would be taken against him.

Under Serbian law, the suspect may not be held criminally responsible as he is under 14.

Police say he planned the attack a month in advance and that he had carried a "priority list" of children to target and which classrooms he would go into first.

Most of the victims were born in 2009 - meaning they were either 13 or 14 at the time of the incident.

A national three-day mourning period starting on Friday has been announced by Education Minister Branko Ruzic, while no school will take place for the rest of Wednesday.

"It is unthinkable when you see the scene of the place, what the children have been through, and the teachers, the teachers who have tried to protect the children," he told a press conference on Wednesday afternoon.

Seven girls and one boy have been confirmed among the dead, with four further boys and two girls injured.

"Sadly there is no possible way for them to come back," Health Minister Danica Gruji?i? said, close to tears. "This is the worst thing I have seen in my whole career as a doctor and as a human being," she added.

A boy who was shot in the neck and chest in said to have suffered the worst injuries, while a girl is in critical condition with a head injury.

Three other boys suffered injuries to their the legs, while a second girl was shot in the abdomen and is currently stable.

"There's been an operation and all that can be done [has been] but they're still fighting for her life", the health minister said.

A teacher injured in the attack was also reported to be undergoing surgery and the minister said her life was at risk.

The sounds of crying parents could be heard on the streets around the school hours after the shooting.

Milan Milosevic, the father of one of the pupils at the school, said his daughter was in the class where the gun was fired and managed to escape.

"[The boy] first shot the teacher and then he started shooting randomly," Mr Milosevic told broadcaster N1.

"I saw the security guard lying under the table. I saw two girls with blood on their shirts. They say he [the shooter] was quiet and a good pupil. He recently joined their class."

"I saw kids running out from the school, screaming. Parents came, they were in panic. Later I heard three shots," one student told the Serbian state broadcaster RTS.

Mass shootings are comparatively rare in Serbia, which has very strict gun laws, but gun ownership in the country is among the highest in Europe.

The western Balkans are awash with hundreds of thousands of illegal weapons following wars and unrest in the 1990s. In 2019, it was estimated that there are 39.1 firearms per 100 people in Serbia - the third highest in the world, behind the US and Montenegro.

In the deadliest shooting since then, Ljubisa Bogdanovic killed 14 people in the central village of Velika Ivanca in 2013, and Nikola Radosavljevic killed nine and wounded five in the eastern village of Jabukovac in July 2007.