Two Indian-origin Madhesis were shot and killed by the Nepal police during a protest that created a blockade of a key highway. The protests were against the new constitution, officials said Sunday, as violence has once again returned to the nation due to a shortage of essential goods.

An indefinite curfew has been initiated in the Saptari district, which is located some 280 kilometres southeast of the capital, after the two protesters were shot Saturday night on the East-West Highway, according to The Times of India.

Apart from the two shot, several other protesters and two policemen were said to be in critical condition. More than 40 people, including 25 policemen, are said to have been injured in the clash. The Saptari Superintendent of Police Bhim Dhakal said that they were forced to open fire after 2,000 agitating Madhesi Morcha activists started attacking police and escorted vehicles using home-made weapons. The protesters have been intercepting and blockading trucks from neighboring India for more than two months, which has resulted acute shortages of fuel and medicine.

The protests come a day after U.N. Secretary General Ban-Ki-Moon showed his distress over the destruction of medical supplies to Nepal due to the ongoing blockade at key border trade points with India. The groups involved in the conflict include the Madhesi and the Tharu ethnic minorities, according to the Rapid News Network.

Indian External Affairs Minister Vikas Swarup said that his government was "distressed at (a) loss of lives in police firing," citing that a political solution was needed.

The Nepalese authorities have been rationing gasoline for taxis and public buses, but private vehicles remain without fuel. Police have so far been escorting cargo trucks and people during the night to escape the violence, but talks between the protesting groups and government have not made any progress, although both sides claim they will continue.

Prime Minister Khadga Prasad Oli will call for a meeting of the main political parties later on Sunday to discuss the Madhesi demands, according to Lancaster Online.