Locals said the incident took place when the ferry was on its way to Madattari under Fakirganj police station from Dhubri town. The ferry was caught up in a heavy storm, they said.
While some people were rescued by locals, most were still missing and rescue operations were on.
Dhubri Superintendent of Police P Saloi, who confirmed the incident, said that the number of casualties could not be immediately ascertained.
“Rescue operations are going on with the help of BSF personnel. We have also called in the services of the National Disaster Response Force,” said Saloi.
Meanwhile, Prime Minister Manmohan Singh expressed grief over the tragedy. “The Prime Minister is shocked and grieved to know about the loss of lives in a boat tragedy on the Brahmaputra river in Assam,” said an official release.
The Prime Minister spoke to Assam Chief Minister Tarun Gogoi to convey his condolences and expressed solidarity with the people of the northeastern state.
The Prime Minister is a Rajya Sabha MP from Assam.