Nepal's troubled south votes Thursday in historic elections many hope will bring much-needed stability to the desperately poor country, but which have been marred by violence and fears of ethnic tension.

The watershed vote marks Nepal's transition from a monarchy to a federal democracy, after emerging from a brutal decade of civil war only to stagger through political turmoil and natural disaster.

Thousands of police and soldiers had been deployed ahead of polling day in the capital Kathmandu and the populous lowlands, with the build-up to the vote hit by violence that has left one dead and dozens injured.

The south is home to a mosaic of ethnic minorities who say a new post-war constitution denies them political representation, a cause that has sparked bloody protests in recent years.

More than 12.2 million people are eligible to vote in the the second phase elections, which come 10 days after the country's mountainous north cast their ballots.

The streets of Kathmandu were eerily quiet as polls opened, with vehicles banned from the roads due to security concerns.

The vote will elect the country's first provincial assemblies, devolving power away from a top-heavy central government that has cycled through 10 leaders in the last 11 years.

"Now there will be specific people responsible for different parts of the country it will be more accountable," said Bishwa Shrestha, 46, after casting his ballot in Kathmandu.

The newly-elected assemblies will be tasked with naming their provinces, which are currently referred to by number, as well as choosing capitals and negotiating budgets with Kathmandu -- all sensitive considerations that could rekindle tensions in the ethnically-diverse south.

"How the politics will unfold will depend on how the new parliament addresses the problems and how well the provinces can function," said political analyst Chandra Kishor Jha, referring to the challenges facing Nepal as it enters uncharted territory as a federal state.

"If they cannot fulfil their promises then the groups that have been part of the struggle will not stay quiet. There is possibility of conflict again."

- Politically marginalised -

Years of political turbulence have hampered development in the impoverished Himalayan nation, which is still recovering from a powerful earthquake that hit two years ago, killing 9,000 people and destroying over half a million homes.

It took nine years after the end of a decade-long civil war to agree to a new constitution. The charter adopted in 2015 mandated a sweeping overhaul of Nepal's political system to give greater autonomy to the provinces.

But it also sparked deadly protests in the south by ethnic minority groups who say it leaves them politically marginalised, and have demanded amendments to the charter.

The Communist CPN-UML party is expected to sweep the polls, buoyed by its alliance with the main Maoist party comprised of former rebels who fought government forces for a decade.

But the nationalistic CPN-UML has strongly opposed amending the constitution to address the demands of ethnic minorities that it views as being more closely aligned with India.

Many in the southern lowlands share close linguistic and cultural ties with Indians across the border.

Nepal's powerful neighbour to the south has long played the role of big brother in the landlocked country.

But in recent years Kathmandu has played diplomatic ping-pong with its two large neighbours, India and China, who use big-ticket infrastructure projects to vie for influence.

Counting of ballot papers from both phases of the elections will begin once polling stations close at 5pm (1115 GMT). Results are expected in the next few days.