Story highlights Tawakkul Karman is the first Arab woman to win the peace prize

The prize is divided between three women; two in Liberia and one in Yemen

Johnson Sirleaf says she accepts the prize on behalf of all Liberians

Rights group Amnesty International welcomes the award

Liberian President Ellen Johnson Sirleaf, activist Leymah Gbowee of Liberia and rights activist Tawakkul Karman of Yemen share this year's Nobel Peace Prize, the Norwegian Nobel Committee announced Friday.

They were chosen "for their nonviolent struggle for the safety of women and for women's rights to full participation in peace-building work," the committee said in Oslo, Norway.

"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."

In an interview with CNN, Karman -- the first Arab woman to win the Nobel Peace Prize and one of the youngest recipients -- said she heard the news while demonstrating in the Yemeni capital, Sanaa.

"Congratulations to all the Yemeni people. I am so happy for the award. I believe this award is for all Yemenis, for all the Yemeni people, and for all Arab women," she said.

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"This is a victory for peace in the Arab world, a victory for the peaceful revolution in Yemen."

Johnson Sirleaf, Liberia's 72-year-old president and Africa's first elected female head of state, told CNN she was excited about the prize, which she said was shared by all her country's people.

"I'm accepting this on behalf of the Liberian people, so credit goes to them," she said. "For the past eight years, we have had peace and each and every one of them has contributed to this peace."

She said the peace that had ended 14 years of civil war should be attributed to the country's women.

They were "women from all walks of life who challenged the dictatorship of former President Charles Taylor and who stayed out in the sun and the rain working for peace in our country," she said.

Johnson Sirleaf, whose political resilience and tough reputation have earned her the nickname "Iron Lady," is campaigning for re-election.

The Harvard graduate's commencement address in high school in 1972 sharply criticized the government, a rare defiance in Africa, especially at the time. She has also worked at the World Bank and the United Nations.

Her historic 2006 election win was a major milestone for Africa, a continent dominated by male dictators who are referred to as strongmen. The mother of four sons published a book, "This Child Will Be Great" in 2008.

Liberian Information Minister Cletus Sieh told CNN that Johnson Sirleaf is a role model for many women in Africa.

Gbowee, a founder and executive director of Women Peace and Security Network-Africa, was also a recipient in 2009 of the John F. Kennedy Profile in Courage Award.

She was the focus of the documentary "Pray the Devil Back to Hell," which shows how women confronted Taylor with a demand for peace to end the bloody 14-year civil war.

She "mobilized and organized women across ethnic and religious dividing lines to bring an end to the long war in Liberia," the Nobel committee said, adding she also encouraged women's participation in elections.

"She has since worked to enhance the influence of women in West Africa during and after war," it said.

Jan Egeland of Human Rights Watch told CNN the Nobel committee had come up with a great prize that merged the efforts of Liberian women in achieving "momentous change" in their country with the vital role of women in the ongoing Arab Spring movement.

Rights group Amnesty International said the award would encourage women everywhere to continue fighting for their rights.

In Yemen, Karman has played a leading role in the struggle for women's rights for democracy and peace, the committee said.

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Karman is the president of Women Journalists Without Chains, a group campaigning for press freedom.

Abdu Ganadi, spokesman for Yemen's President Ali Abdullah Saleh, congratulated Karman but struck a warning note.

"We are happy that she won, but in the same time she needs to live up to the award and not take youths to protests in areas where it leads to bloodshed," he told CNN. "She has to be a caller for peace, not violence."

Mohammed al-Sabri, a spokesman for Yemen's opposition dialogue committee, highlighted her role in an ongoing protest involving more than 3 million young Yemenis, many of them women.

"Because of Karman, the world will have a different impression on Yemeni women," he said. "This prize is not only for her, but for all Yemeni women."

Mohammed Albasha, a spokesman for Yemen's embassy in Washington, D.C., told CNN: "To have the first Arab woman to win a Nobel Peace Prize be from Yemen is definitely an honor to all Yemeni women."

Prominent Yemeni human rights activist Khaled Al-Anesi, who is also heavily involved in anti-government demonstrations, said he was very happy Karman had won the award.

"I feel this is a reward for every Yemeni looking for peace, for freedom, for democracy," he said. "The Nobel Peace Prize will bring attention to our revolution, which doesn't have enough international attention and attention from the foreign media."

Yemeni online activist Atiaf Alwazir said it was "great news for Yemen."

"Tawakkol has become such a figure in the revolution. It's a prize for Yemen -- it's a prize for all Arab women and it's a show of international support and solidarity for the peaceful movement here," she said.

"I'm very happy she received this award, as a woman and as an activist. It shows that if you work hard enough, maybe the world will listen. I think the best thing about this is that it's for everybody.

"An award like this is really a way to restore faith in the peaceful movement and to give people moral support. After nine months, people here are tired, and this gives people hope."

A profile of Karman by Time magazine describes the mother of three as "Yemen's most active activist."

As well as leading demonstrations demanding freedom of speech, she can often be seen trying to get other protesters out of jail. "It's a place she is familiar with as well, having been there several times herself," the profile says.

The Norwegian Nobel Committee said it hopes that the prize will help end suppression of women in many countries and to "realize the great potential for democracy and peace that women can represent."

The award, which includes a cash prize (10 million Swedish kronor, or about U.S. $1.4 million) will be shared in three equal parts among the winners, the committee said.

"This Nobel Peace Prize recognizes what human rights activists have known for decades: that the promotion of equality is essential to building just and peaceful societies worldwide," said Amnesty International Secretary General Salil Shetty in a statement.

"The tireless work of these and countless other activists brings us closer to a world where women will see their rights protected and enjoy growing influence at all levels of government."

European Council President Herman Van Rompuy and European Union President Jose Manuel Barroso congratulated the winners.

They issued a statement saying the prize is "recognition of the pivotal role that women play in the peaceful settlement of conflicts and democratic transformation throughout the world. This is a victory for a new democratic Africa and for a new democratic Arab world that live in peace and respect for human rights."

Last year, Chinese dissident Liu Xiaobo won the prize but could not attend the award ceremony. The political activist and longtime critic of communist rule in China is serving an 11-year prison term for what the Chinese government calls "inciting subversion of state power."

U.S. President Barack Obama won for what the committee called "his extraordinary efforts to strengthen international diplomacy and cooperation between peoples" in 2009.

Nobel prizes in literature, chemistry, physics and physiology or medicine were awarded this week.

The Nobel Peace Prize is awarded by a committee of five people chosen by Norway's parliament and is named for Alfred Nobel, a Swedish scientist and inventor of dynamite.

Nominations come from lawmakers around the world, university professors, previous Nobel laureates and members of the Nobel committee.