Thousands of litres of oil have spilt into the protected Sundarbans mangrove area, home to rare Irrawaddy and Ganges dolphins, after a tanker collided with another vessel last Tuesday.
A team from the United Nations Disaster Assessment and Coordination (UNDAC) has arrived in the capital Dhaka to support Bangladesh's "cleanup efforts of the oil spill in the Sundarbans", a statement from the UN said.
Until now, the forest department was relying on villagers and fishermen to scoop up the thick tar from the water and river banks with sponges and pans.
The UN team will help in the "ground work in coordination with the government" and "will also conduct an assessment and advise on recovery and risk reduction measures", it said, adding the team had been sent in response to a request from Bangladesh.
The European Union and United States, Britain and France are supporting the UN effort, it added.
