Franz Adlkofer, who led the Reflex study, said people should use landlines, rather than mobiles, wherever possible.

He added: "We don't want to create a panic, but it is good to take precautions."

He said definitive research would take another four to five years.

[snip]

"The results of this study are preliminary, not yet published or peer-reviewed and require further replication by other groups."