Helicopter sightseeing flights over the famous Gold Coast on Australia's east coast have ended in tragedy: two helicopters collided in the air near Sea World theme park early Monday afternoon (local time). At least four people were killed and three others are in critical condition, police spokesman Gary Worrell said. According to initial findings, one of the helicopters had just taken off and the other was about to land when the rotors came into contact.

A helicopter then crashed and landed upside down on a sandbank in the sea. Numerous pieces of debris could be seen in the pictures. The other managed to land, but the windshield broke. Six occupants were injured by broken glass, it said.

The accident happened near Sea World Marine Park on Main Beach. The helicopters are said to be part of the theme park and have been used for sightseeing tours. Sea World was "shocked by what happened," a spokesman said. "Our sincere condolences go to all those involved and in particular to the relatives and families of the deceased."

A large contingent of police and paramedics were deployed. An eyewitness told broadcaster 9News: "I don't know exactly what happened, but there was a massive bang." Queensland Prime Minister Annastacia Palaszczuk called it an "unimaginable tragedy".

Immediately after the accident, people on boats and jet skis rushed to help those affected, the AAP news agency reported. How exactly the collision could have happened was initially unclear. The Australian Transport Safety Authority began investigations.