The first African woman and the first environmentalist to have taken the coveted prize, Maathai, 64, was selected by the Nobel committee for her campaign to save Africa's forests, which began with nine trees in her yard nearly three decades ago.

Maathai, who won the prize on October 8, will receive the award, plus 10 million Swedish kronor (1.1 million euros), in an official ceremony on Friday, the anniversary of the death of prize founder Alfred Nobel.

As she stepped off her plane at Oslo's international airport, Maathai stressed the importance of the environment for world peace.

"Many of the wars that are fought in the world are fought over natural resources," she said.

Maathai, Kenya's assistant minister for the environment since 2003, is the founder of the Green Belt Movement, the largest tree planting project in Africa, aimed at promoting biodiversity, job creation and giving women a stronger identity in society.

"Planting trees ... stops soil erosion, it stops the wind erosion, it helps to stabilise the land, so, yes, it keeps the deserts away," Maathai said.

Deforestation has been a major problem in Kenya, exposing millions of people to drought and poverty.

The Nobel Committee's decision reflects environmentalism's extraordinary rise from the wings to the centre stage of politics, and was hailed by ecologists the world over.

Time magazine had already made her "Hero of the Planet" in 1998 and she is a household name in her country.

The latest Nobel laureate is also a human rights activist in Kenya, and her opposition to the one-party rule of former president Daniel arap Moi led to her being jailed, harassed and vilified.

Maathai will receive the Nobel prize at a ceremony in Oslo's city hall from Nobel committee president Ole Mjoes in the presence of Norway's King Harald.