German Chancellor Angela Merkel and US Secretary of State Hillary Clinton led a chorus of praise from world leaders and rights groups for the awarding of the Nobel Peace Prize Friday to three women who have fought for women's rights.

Liberian President Ellen Johnson Sirleaf, her compatriot and "peace warrior" Leymah Gbowee and Yemen's Arab Spring activist Tawakkul Karman were announced as the joint winners in Oslo.

Norwegian Nobel Committee president Thorbjoern Jagland said the trio shared the award "for their non-violent struggle for the safety of women and for women's rights to full participation in peace-building work."

Merkel, recently named the world's most powerful woman for the fourth time by Forbes magazine, described the award as a "very good signal".

"It will hopefully encourage many women -- and also many men -- worldwide to fight for freedom and democracy and against injustice," the chancellor said.

She reserved a special mention for Karman -- the first Arab woman to win the prize.

"The lady from Yemen is still in a situation where she is not free and therefore I would like to praise her courage especially," Merkel said.

Karman, a 32-year-old journalist and activist with three children, has braved several stints in prison in her campaign for women's rights, press freedoms and the release of political prisoners in her country.

Clinton on Friday praised the awarding of this year's Nobel Peace Prize to three women as "an inspiration for women's rights and human progress everywhere."

Clinton, a longstanding champion of women's rights, paid tribute to the Liberian president, Gbowee and Karman, saying they were "shining examples of the difference that women can make and the progress they can help achieve when given the opportunity to make decisions about the future of their societies and countries".

"This recognition of their extraordinary accomplishments reflects the efforts of many other women who are promoting peace and security in their countries and communities," Clinton said in a statement.

British Foreign Secretary William Hague welcomed the "historic" award. "These three women are a clear example of what can be done to change the world for the better," he said in a statement.

UN chief Ban Ki-moon said the winners had "uncommon courage, strength and commitment", adding: "With this decision, the Norwegian Nobel Committee sends a clear message: women count for peace".

The Vatican hailed the choice as a "noble and encouraging" sign.

Women, Peace and Security Network Africa, the Ghana-based non-governmental founded by Gbowee, said the Nobel recognition would boost the women's movement in Africa and beyond.

"We are spreading our wings all over the world now because now we have a star," administrative manager Bertha Amanor said.

Gbowee is credited with leading women to defy feared warlords and push men toward peace in Liberia during one of Africa's bloodiest wars.

South Africa's Desmond Tutu, who won the Nobel in 1984, said Johnson Sirleaf deserved it "many times over".

"She's brought stability to a place that was going to hell," he said after leaving a church service to celebrate his 80th birthday.

Bono, the campaigning U2 frontman, said the Liberian president was the "most extraordinary woman" and he felt "so lucky to have worked with her over the years, cancelling Liberia's debt".

French President Nicolas Sarkozy described the laureates as "exceptional women" and hailed Johnson Sirleaf as "a symbol of democracy in Africa".

Karman's share in the prize was "a tribute to the Arab peoples who are expressing with courage their hopes for liberty and democracy, hopes that the president fully supports", Sarkozy's office said.

Former Polish president Lech Walesa, himself a winner in 1983 for leading Solidarity, the Soviet bloc's first and only free trade union, said the award for Karman could inspire other Arab women.

"Women from Arab countries can be particularly encouraged in fighting for their rights -- there's still a lot to do. Democracy isn't built in a day," he told AFP.

For Amnesty International, the award was vital recognition of the struggle for women's rights.

"This Nobel Peace Prize recognises what human rights activists have known for decades: that the promotion of equality is essential to building just and peaceful societies worldwide," said Amnesty secretary general Salil Shetty.

Human Rights Watch said the decision "recognises that democracy and lasting peace cannot be achieved without giving women the full opportunity to participate".

The Elders, an independent group of global leaders brought together by Nelson Mandela in 2007, including former UN chief Kofi Annan and former Finnish and US presidents Martii Ahtisaari and Jimmy Carter -- both Nobel Peace Laureates -- said they were "delighted" with the choice.

"Women play an equal role with men in conflict resolution and peace-building. The Nobel Peace Prize for 2011 acknowledges the leadership of women as powerful agents of change," they said in a statement.

The European Union, a losing nominee for the award, hailed the "pivotal role" played by women in conflict resolution as they congratulated the winners.

The one voice of discord came from the Liberian leader's rival in Tuesday's presidential election, Winston Tubman, who accused her of "committing violence".

"This award is unacceptable and undeserving," he said.

burs-gj/ach/gk