(Reuters) -- Nepali police shot and killed an Indian citizen at a border checkpoint on Monday as they tried to clear protesters whose blockade has strangled Nepal's fuel supplies and badly damaged relations between the neighbors.
Nepal has faced an acute fuel crisis for more than a month since protesters in the lowland south, angered that a new constitution fails to reflect their interests, prevented supply trucks from entering from India.
Indian Prime Minister Narendra Modi condemned the killing of an Indian youth and spoke with Nepal's Prime Minister KP Oli to seek details about the incident.
Many in Nepal see India's hand in the protests although it denies any role.
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Modi said he had assured the Nepalese leader that there was "no obstacle" from India to the supply of fuel and other essentials to Nepal.
With the landlocked Himalayan nation of 28 million recovering from its worst earthquake on record, the government has turned to China for extra fuel. Officials said some Chinese oil was due to arrive in Kathmandu late on Monday.
Hundreds of stick-wielding protesters battled with police near the border crossing, known as the "friendship bridge", in Birgunj district, television pictures showed.
Raju Babu Shrestha, district police superintendent, said protesters threw petrol bombs and stones at a police post prompting them to "fire in self defence".
"One protester, an Indian national, who was attacking the police post with the petrol bomb was killed in the firing," Shrestha said, adding that the man was killed a few hundred metres from the border crossing.
More than 20 people including 15 police officers were injured in the clash, he said.
Indian foreign ministry spokesman Vikas Swarup said India was deeply concerned about the violence in which "an innocent Indian" was killed. He said Indian fuel-truck drivers were advised not to put themselves in danger.
Protests over a new constitution turned violent in August and more than 40 people have been killed as southern plains dwellers objected to seeing their lands divided and included in several federal states dominated by mountain communities.
The constitution was nonetheless adopted on Sept. 20, paving the way for the formation of a government headed by Prime Minister K.P. Oli, who has failed to calm passions that have paralysed economic and political life.
Earlier on Monday, police cleared protesters staging a sit-in on the bridge but a protest leader said they had re-occupied it and five people had been hurt.
The protesters had gone into Birgunj town where they were burning tyres. A protest leader, Purushottam Jha, from a political party that represents minority Madhesis, said police had used teargas in the town and fired into the air.
Police said 219 empty trucks had been cleared to return to India but that none had entered from India.