More than two dozen people suffered from carbon monoxide poisoning during a dinner in a dome tent at a campsite in central Switzerland, police said on Sunday.

"Late on Saturday evening, a number of people in Giswil suffered from carbon monoxide poisoning and had to be hospitalised," regional police in Obwalden canton said.

The incident occurred during a large private dinner party in a dome tent at the Giswil campsite.

At around 10:30 pm (2130 GMT), a number of the 35 people in attendance suddenly lost consciousness and others complained they felt unwell, Obwalden police said, adding that the group had immediately gone out into the fresh air.

"According to initial investigations, there was an excessive accumulation of carbon monoxide in the tent over the course of the evening, causing a number of people to suffer from carbon monoxide poisoning," the police said.

"Twenty-six people were hurt in the incident, with 17 people having to be hospitalised."

First responders and rescue workers, along with two rescue helicopters, were deployed to the scene.

Police said they were investigating what caused the increased accumulation of gas in the tent, in cooperation with the Zurich Forensic Institute.