Thousands of so-called "honour" killings take place every year around the world.

Activists think the number is significantly higher than those reported in each country.

Research done by a leading American academic and reviewed independently by human rights organisations, now sheds light on how these crimes occur.

Source for data: Phyllis Chesler, Emerita Professor of Psychology and Women's Studies at City University of New York, on worldwide trends for "honour" killings. Published in The Middle East Quarterly.