Google is celebrating International Women's Day with a doodle with symbols of women replacing its familiar logo.

The "G" in Google on the search engine's homepage has been replaced with the female symbol while one of the "o" has been substituted with a flower.

Clicking on the doodle brings up a search results page for International Women's Day.

International Women's Day has been observed since in the early 1900s. This year's event - the 101st – will be marked by thousands of events worldwide that celebrate women's progress or rally against inequality.

World leaders including Barack Obama and UN Secretary-General Ban Ki-moon are lending their support to the event. British prime minister David Cameron is to call for the elimination of violence against women and girls.

Celebrities involved in the day's events include former Eurythmics singer Annie Lennox, Oscar-winning actor Reese Witherspoon and Sex and the City star Kristin Davis, and model and photographer Helena Christensen.

Last year's Google doodle for the hundredth anniversary of the event incorporated an interactive map inviting users to join thousands of people worldwide to show their support for women's causes.