LONDON (Reuters) - Greek researchers called yesterday for more safety studies into electronic cigarettes, saying scientific knowledge of them was "very limited".

Electronic cigarettes, or e-cigarettes, were first made in China and are sold mostly on the Internet.

They are battery-powered devices which emit a "puff" or fine mist of nicotine into the lungs and are intended to replace normal cigarettes and help smokers quit.

The products are at the centre of a legal battle in the United States between manufacturers and the Food and Drug Administration (FDA), which regulates drugs and which wants to stop e-cigarettes from being imported into the US.

The FDA, which conducted research into e-cigarettes, has expressed concerns about their safety, and teams from Greece and New Zealand have also carried out studies into them.

But interpretations of the three reports vary, with the New Zealand study saying e-cigarettes should be recommended because they are safer than tobacco cigarettes, and the Greek study taking a broadly neutral stance.

"The limited information given in these three reports represents all the knowledge we currently have about e-cigarettes," Andreas Flouris and Dimitris Oikonomou, of the Institute of Human Performance and Rehabilitation in Greece, wrote in the British Medical Journal.