Two children have died and several have been left critically injured after they fell about 10 metres from a jumping castle that was blown into the air in north-west Tasmania.

Police and emergency services were alerted to a serious incident at Hillcrest Primary School in Devonport around 10am on Thursday.

Commander Debbie Williams was speaking at the school this afternoon and described the scene as “distressing”.

“Tragically I can confirm that there are two deceased children after an incident today at Hillcrest Primary School,” Commander Williams said.

“This is a very tragic event and our thoughts are with the families and the wider school community, and also our first responders.

“There is no doubt that this has been a very confronting and distressing scene.

“Counselling is being made available to the families affected by this in the school community along with the first responders.”

Several rescue helicopters were used to transport the children, while police units and multiple ambulance crews are at the scene.

People have been told to avoid the area.

The school announced on Facebook it was closing for the remainder of Thursday and asked parents to urgently collect their children.

The school was holding a ‘Big Day In’ celebration to mark the end of the school year.

Prime Minister Scott Morrison described the events as “shattering”.

“The events that occurred today in Devonport in Tasmania are just shattering. They are just unthinkably heartbreaking.

“Young children on a fun day out, together with their families and it turns to such horrific tragedy, at this time of year, it just breaks your heart.”

He said he had spoken to premier Peter Gutwein, who was on his way to Devonport, to offer his full support.

“I just want to say, to the parents and families and friends, all who were there, to the other young children there … I just pray you’ll have great family around you and great friends and you can come through this horrific tragedy.”