OSLO - Three women who have campaigned for rights and an end to violence in Liberia and Yemen, including Liberian President Ellen Johnson-Sirleaf, won the Nobel Peace Prize on Friday, the head of the Norwegian Nobel Committee said.

Another Liberian, Leymah Gbowee, who mobilised fellow women against the country's civil war including by organising a "sex strike", and Tawakkul Karman, who has worked in Yemen, will share the prize worth $1.5 million with Johnson-Sirleaf, who faces re-election for a second term as president on Tuesday.

"We cannot achieve democracy and lasting peace in the world unless women obtain the same opportunities as men to influence developments at all levels of society," Committee chairman Thorbjoern Jagland told reporters.

"The Nobel Peace Prize for 2011 is to be divided in three equal parts between Ellen Johnson-Sirleaf, Leymah Gbowee and Tawakkul Karman for their non-violent struggle for the safety of women and for women's rights to full participation in peace-building work."

Johnson-Sirleaf, 72, is Africa's first freely elected female president. Gbowee mobilized and organized women across ethnic and religious dividing lines to bring an end to the war in Liberia, and to ensure women's participation in elections. ?

The Committee added: "In the most trying circumstances, Tawakkul Karman has played a leading part in the struggle for women's rights and for democracy and peace in Yemen."

"It is the Norwegian Nobel Committee's hope that the prize to Ellen Johnson-Sirleaf, Leymah Gbowee and Tawakkul Karman will help to bring an end to the suppression of women that still occurs in many countries, and to realise the great potential for democracy and peace that women can represent."