Prostate cancer may be a sexually transmitted disease, researchers have claimed.

They say this type of cancer could in some cases be caused by an infection transmitted during during sex.

Researchers at the University of California tested human prostate cells in a laboratory setting.

They found a sexually-transmitted infection called trichomoniasis can progress cancer growth.

This bug is believed to infect some 275 million people worldwide and is the most common sexually transmitted infection not caused by a virus

It tends to be a silent infection - often, a person will have no symptoms and be unaware that they have it.

However, they say more research is necessary to confirm the link between this infection and cancer of the prostate. The research is reported in the journal Proceedings of the National Academy of Sciences (PNAS).