KATHMANDU - A Swiss trekker was injured after being beaten by Nepal's former Maoist rebels because he refused to pay a "donation", an official said on Friday, the first known assault of a foreigner by the Maoists.

Police said 31-year-old Steve Jeanneret was attacked at Birethanti, 150 km (93 miles) northwest of Kathmandu, on the Annapurna trekking trail, a popular route for Western trekkers in Nepal, after refusing to pay $28 to the former rebels.

"He was stopped by two Maoist activists who asked for the donation and was beaten up by bamboo sticks," Sharad Pradhan, a spokesman of the Nepal Tourism Board said.

Jeanneret told the Maoists that he had read in newspapers that their chief Prachanda had said donation to the ex-guerrillas was not compulsory and refused to pay them, according to Pradhan.

"The Maoists then beat him up. His head is injured," Pradhan said adding that the trekker's Nepali guide was also manhandled.

Jeanneret has now returned to western resort town of Pokhara.

There was no immediate comment from the Maoists who ended their decade-long civil war under a peace deal last year.

Human rights activists and many politicians accuse the Maoists of continuing extortion, intimidation and abductions despite joining the peace process.

The Maoists say their policy was not to harm foreign tourists, a key source of income for the impoverished country known for its scenic beauty and home to eight of the world's 14 highest mountains including Mount Everest.

Although the Maoists collected money from the visitors there were no reported cases of their activists beating up foreign tourists even during the war which started in 1996.

Officials say tourism industry that was badly hit during the conflict has begun to grow after the war ended.

More than 13,000 people were killed in the insurgency.