Regular use of mobile telephones increases the risk of developing tumours, a new scientific study by Israeli researchers and published in the American Journal of Epidemiology revealed on Friday.

An extract of the report seen by Israel's Yedoit Aharonot newspaper put the risk of developing a parotid gland tumour nearly 50 percent higher for frequent mobile phone users -- more than 22 hours a month.

The risk was still higher if users clamped the phone to the same ear, did not use hands-free devices or were in rural areas.

"Analysis restricted to regular users or to conditions that may yield higher levels of exposure (eg heavy use in rural areas) showed consistently elevated risks," said an abstract of the report in the US journal made available to AFP.

The study included 402 benign and 58 malignant incident cases of parotid gland tumour diagnosed in Israel at age 18 years or more, in 2001-2003.

The research was led by Dr Siegal Sadetzki, a cancer and radiation expert at the Chaim Sheba Medical Centre in Israel and as part of a World Health Organisation project.