Kenyan police fired tear gas into a crowd of Nairobi schoolchildren Monday as the youngsters and adults protested against what they call an illegal confiscation of a playground.

A police spokesman said authorities were investigating the incident and planned to initiate disciplinary proceedings against the officers involved.

“Apparently a level of force which is not commensurate to the persons involved was used,” said Masoud Mwinyi, adding that four adults had also been arrested.

Police were seen firing at least three canisters of tear gas just outside the Langata Primary School as several hundred students attempted to knock down a wall surrounding the playground.

They were protesting what they called an illegal “land grab” and a plan to turn the space into a car park.

Children wearing bright green school uniforms dashed away from the scene, some coughing and choking and covering their faces with bits of clothing. Activists said they believed eight children were hospitalized for exposure to tear gas and other injuries.

“They were trying to access that playground, and it’s actually their playground,” said activist Boniface Mwangi, who took part in the protest. “We are very happy that the kids were brave enough to bring down the wall.”

A jubilant crowd of children eventually made their way onto the land, where they danced and began an impromptu soccer match.

Many Kenyans took to social media to express outrage over the incident, using the Twitter hashtag “OccupyPlayGround.”