The use of mobile phones over a long period of time can raise the risk of brain tumors, a Swedish study, quoted by Reuters, said.
The report said the new study contradicted the conclusions of other researchers.
Reports said last year that the Dutch Health Council, in an overview of research from around the world, found no evidence that radiation from mobile phones and TV towers was harmful, the report said.
A four-year British survey in January also showed no link between regular, long-term use of cellphones and the most common type of tumor, the report added.
But researchers at the Swedish National Institute for Working Life looked at mobile phone use of 2,200 cancer patients and an equal number of healthy control cases, the Reuters report said.
The report said that of the cancer patients, aged between 20 and 80, 905 had a malignant brain tumor and about a tenth of them were also heavy users of mobile phones.
The study defined heavy use as 2,000 plus hours, which "corresponds to 10 years' use in the work place for one hour per day," the report said.
Early use was defined as having begun to use a mobile phone before the age of 20, the report added.