Two tourists kayaking on a lake in New Zealand's South Island have been reported dead, after being hit by strong winds that tipped them into the cold water.

Nine other people were rescued in the incident at Lake Tekapo, a popular tourist destination.

Despite wearing life jackets, those rescued are suffering from hypothermia and some have been taken to hospital, police said in a statement.

The victims have been identified as James Murphy, 20, from London and 21-year-old Daniel Hollnsteiner from New York state.

Philosophy student Mr Murphy was on an exchange trip from Warwick University, in Coventry.

Police Inspector Dave Gaskin, the mid-south Canterbury area commander, told Radio New Zealand that the kayaks were "swamped" after a sudden weather change.

The temperature in the lake was about 3C, and it would have been even colder with the winds, he said, according to the New Zealand Herald.

Police say an investigation will take place into the incident.

In October 2009, three men drowned on the lake after crashing their boat into what was thought to be a log.