A motorcycle set on fire by protesters in Rupni of Saptari district on Sunday, November 22, 2015. Photo courtesy: The Himalayan Times

AFP/Kathmandu

Nepalese police shot dead two protesters after fresh clashes erupted in the country's southern plains as a crisis over a new constitution deepens, a local senior officer said Sunday.

The clashes broke out late on Saturday in the southeastern district of Saptari as protesters armed with batons and home-made tools tried to block a highway in defiance of police orders, the officer said.

"Two were killed in the police firing," district police chief Bhim Dhakal told AFP.

"The police were forced to fire after the protestors became violent and attacked," adding that more than 40 protesters and police were also injured in the unrest.

Nepal is heavily dependent on India for fuel and other supplies, but little cargo has crossed the border from India since protests against the new constitution broke out in late September.

As a nationwide fuel shortage deepens, medical supplies are now also running dry in the impoverished, landlocked country.

UN Secretary-General Ban Ki-moon on Friday urged protesters to stop blocking essential supplies and called for dialogue to resolve the crisis.

More than 40 people have been killed in clashes between police and people protesting against the constitution, which was introduced in September after a deadly earthquake pushed warring political parties to reach agreement.

Demonstrators from the Madhesi ethnic minority, mainly from the southern plains, have been blockading the main Birgunj border crossing, protesting the new constitution they say leaves them politically marginalised.

Movement across other border checkpoints has also slowed to a crawl, prompting fuel rationing and forcing the government to start selling firewood as residents run out of cooking gas.

Nepal's government accuses India, which has criticised the new constitution, of retaliating with an "unofficial blockade".

New Delhi has denied the charge and urged dialogue with the protesting Madhesis, who have close cultural, linguistic and family ties to Indians living across the border.

Nepal's Prime Minister KP Sharma Oli has warned that the blockade is having an impact "several times more than the quake" that struck in April.

But several rounds of talks between the government and the protesting parties have failed to reach an agreement.

The constitution, the first drawn up by elected representatives, was meant to cement peace and bolster Nepal's transformation to a democratic republic after decades of political instability and a 10-year Maoist insurgency.