India denies imposing a blockade, saying its truck drivers are concerned for their safety after protests inside the Himalayan nation.
In a statement, Nepal's Home Ministry said that an "odd-even system" had been introduced Sunday, meaning "vehicles with odd number plates can only operate on odd dates, and even number plates on even dates."
Ministry spokesman Laxmi Prasad Dhakal acknowledged that dozens of protesters had been injured in protests since the constitution was passed but denied there were major security concerns for the trucks to pass the checkpoints.
Dhakal told CNN demonstrations had been taking place in Nepal for months before the constitution was enshrined and trucks had been entering without major problems.
"Just after the constitution was put into effect, India stops the trucks at the border citing security issues. Our stand is this is a vengeance from India as they are not happy with Nepal's new constitution. This is a trade blockade, just not officially announced," Dhakal said.
The Nepal Oil Corp. said Indian customs and the Indian Oil Corp. had not allowed the majority of trucks to enter Nepal for 10 days.
Nepal now faces a "major fuel crisis situation," with only two to three weeks' supply and more than 400 fuel trucks stuck on the Indian side of the border, NOC spokesman Deepak Baral said.
The fuel crisis appears to have implications beyond Nepal's borders.
Baral said international airlines had been told to carry their own fuel for return trips, and China Southern Airlines on Monday said
it was canceling its flights between Guangzhou and Kathmandu until October 10 due to the shortages.
Nepal enshrined its first constitution written by representatives of the people on September 20. It followed a 65-year battle for increased democratic control in the Himalayan country, where the monarchy and military traditionally held power.
India, Nepal's much larger neighbor, noted the passing of the constitution but expressed concern that some disgruntled groups had not been engaged in passing it.
Lawmakers from opposition parties representing the Madhesi and Tharu indigenous groups boycotted the final voting process. Their main demands were representation equal to their population and federal redistricting that would maintain Madhesi and Tharu provinces -- which would guarantee the groups a bigger representation in parliament.
In a statement issued after the constitution was passed last Monday,
India said it had "consistently argued that all sections of Nepal must reach a consensus on the political challenges confronting them."
It said "incidents of violence" had created difficulties for Indian freight companies and transporters operating in Nepal.
On Friday, the ministry referred to "reports of obstructions at various entry-exit points at the India-Nepal border."
"The reported obstructions are due to unrest, protests and demonstrations on the Nepalese side, by sections of their population," a Ministry of External Affairs spokesman said.
Some Nepalis have responded to India's criticism using the hashtag #backoffindia on social media, asking India to end what they see as its interference in Nepal's domestic politics. Nepali media have been showing images of anti-India protests across the country, with effigies of Indian Prime Minister Narendra Modi being burned at several locations.
Its mountainous geography on the northern side means there are few trading routes with China, and India is its major trading partner.
The massive earthquake
that struck Nepal early this year further disrupted the few available crossings with China.