Just when Nepal thought it had finally put an end to a decade-long civil war between its royalist government and Maoist rebels, which killed more than 13,000 people, up pops a wave of ethnic groups threatening to derail the peace process with violent protests and strikes.

But why? Well, according to an article in the Economist, the ethnic movements are trying to break a centuries'-old stranglehold by the country's top Hindu castes.

Ever since Nepal united in the 18th century, power has alternated between two castes - the Brahmin (priestly) and Chhetris (warrior). King Gyanendra's government which was ousted last year was largely from the Chhetris caste. It has been replaced by a coalition government dominated by Brahmins.

So where do the Maoists fit into the picture?

The Economist says that although they championed the cause of the lower castes and ethnic groups during the conflict, they are mainly led by Brahmins. And now that Maoist leaders have joined the interim parliament, their former supporters from among the lower castes and ethnic groups feel their grievances are being ignored.

Those at the bottom of the Hindu social heap, the dalits or 'untouchables', say the Maoists used to punish high-caste landlords for exploiting low-caste farmers, but these days they're more preoccupied with politics.

"The only way to end the discrimination is by empowering and educating more dalits, but the government has to be seriously committed, otherwise another civil war will start in the country if the neglect continues," activist Ram Singh Karki told the U.N. news service IRIN.

Hence the protests. First came the Madhesi movement, claiming to represent Nepalis from the southern plains. The Madhesis have an advantage over other ethnic groups because they control supply routes to the capital Kathmandu. But they have also come under attack from the Maoists for withdrawing their support.

Then there was the Nepal Federation of Indigenous Nationalities, claiming to represent peoples from the Himalayan foothills.

They're demanding proportional representation in the elections and an ethnic-federalist structure in the new constitution. The government and the Maoists have vaguely agreed to both, but have not yet held promised negotiations with the protestors.

Last month the Special Representative of the United Nations Secretary-General Ian Martin said that if Nepal fails to include traditionally marginalised groups in the peace process, the country will lose a crucial opportunity to address some of the main causes of the conflict. He also said the June elections may not go ahead as planned because of the current level of unrest.

International Crisis Group has warned that, unless these ethnic and caste fissures are addressed, among other issues, "violent conflict may emerge once more".

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