Officers have said the person who was killed was a security guard and those injured were students.

Milan Nedeljkovic, mayor of the central Vracar district where the school is located, said the teacher is fighting for their life.

The seventh-grade student had fired several shots from his father's gun at the Vladislav RIbnikar elementary school in the capital Belgrade, police have said.

Officers in helmets and bulletproof vests cordoned off the area around the school after the shooting at around 8:40am local time (7:40am UK time).

Local media footage from the scene showed commotion outside the school as police removed the suspect, whose head was covered as officers led him to a car parked in the street.

Reports in Serbia say terrified parents have arrived to the school trying to find their children.

Milan Milosevic, the father of one of the pupils at the Vladislav Ribnikar elementary school, said his daughter was in the classroom when the shooting began.

"She managed to escape. (The boy) ...first shot the teacher and then he started shooting randomly," Mr Milosevic told broadcaster N1.

He continued: "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."

Meanwhile, a girl who attends a high school adjacent to Vladislav Ribnikar told state TV RTS: "I saw kids running out from the school, screaming. Parents came, they were in panic. Later I heard three shots."

Casualties are being treated and an investigation into the motives behind shooting is under way, police said in a statement, without elaborating.

Mass shootings are comparatively rare in Serbia, which has very strict gun laws.

But the western Balkans are awash with hundreds of thousands of illegal weapons following wars and unrest in the 1990s.

Serbian authorities have issued several amnesties for owners to hand in or register illegal guns.