Kenya’s deputy environment minister Wangari Maathai has collected the Nobel peace prize for her efforts to help reforest the country.

The minister, who leads an initiative which has planted about 30 million trees across Africa, called for action to fight deforestation after being presented with the prize at the awards ceremony in Oslo.

She said trees must be managed sustainably to safeguard future timber supplies, as well as protect against desertification and erosion.

But the choice of an environmental campaigner for the Nobel peace prize has sparked some controversry, with critics saying environmentalism should not be linked with peacemaking and conflict prevention.