Image copyright AP Image caption Sheryl Sandberg said women should hold half of all important positions

Facebook's highest-ranked woman has said women need to take action to create a more equal world.

Sheryl Sandberg, chief operating officer of the social network site, said women should hold half of the important positions in business.

"If you're thinking about doing something, ask yourself what you would do if you weren't afraid and then do it," she told the BBC.

Ms Sandberg became the first woman on Facebook's board in June 2012.

Last year, she wrote Lean In, a book advising women on how to make progress in the workplace.

"It's really important that since women make up half of the population, women start having half the seats at tables where the decisions are made and that's not where we are today," Ms Sandberg added.

She said women could make "unbelievably effective" business and government leaders, as well as entrepreneurs.

Talking about the wider challenges facing Facebook, Ms Sandberg said the world was going through a "huge technological shift".

"We are in the middle of the fastest adoption of disruptive technology the world has ever seen and that is the mobile phone," she added.