FLIMS, Switzerland (AFP, REUTERS) - Twenty people died after a vintage World War II aircraft crashed into a Swiss mountainside, police said on Sunday (Aug 5).

"The police have the sad certainty that the 20 people aboard perished," police spokeswoman Anita Senti told a news conference.

The plane crashed in a basin at 2,450 metres above sea level on the west side of the Piz Segnas mountain shortly before 5pm on Saturday (11pm Saturday Singapore time).

Among those killed were 17 people from Switzerland and a three-person family from Austria, police said.

The Junker JU52 HB-HOT aircraft was built in Germany in 1939 and is now a collectors' item.