Nepal's top political parties are reaching out to protesters angry about the country's new constitution, after violence in the region bordering India has halted more than 1,000 oil tankers and trucks with essential supplies from entering Nepal.

Officials say nearly 400 Nepalese protesters clashed with police in Birganj, a town on the border with India, on Thursday. They belong to ethnic and religious groups dissatisfied with Nepal's new constitution adopted on Sunday.

Sri Prakash, an Indian official, says 1,500 oil tankers from India used to enter southern Nepal every day from the Jogbani, but there has been no movement for the past three days, raising fear of shortages in the Himalayan nation.

The violence in recent weeks has killed at least 45 people in Nepal.