HIV infections have doubled in ten years in Russia and former Soviet states, due mainly to unprotected sex and injecting drugs, a report said Thursday.

More than 105,000 new infections were recorded in Russia and former Soviet countries in eastern Europe and Central Asia in 2013, up from just under 50,000 in 2004, said the European Centre for Disease Prevention and Control (ECDC) and the World Health Organization.

The number of those who go on to develop AIDS has also tripled in the region, the report said, while the number of deaths from the disease continue to fall in other parts of Europe.

"In Eastern Europe, where 77 percent of all new infections were reported, two thirds of cases among injecting drug users were detected late. This means they are more likely to transmit HIV, their treatment is more expensive, and they are more likely to die," said Zsuzsanna Jakab, WHO Regional Director for Europe.

The majority of new HIV cases are among people 30 to 39 years old, with Russia and Ukraine reporting the highest number of new infections.

Infection rates also quadrupled in Armenia and Azerbaijan.

The WHO says there were some 35 million people around the world living with HIV by the end of 2013, with some 2.1 million new infections during the course of that year.

Sub-Saharan Africa is the most affected region, with almost 70 percent of new infections.