Bangladeshi fishermen began cleaning up a huge oil spill in a protected area using sponges and sacks yesterday.

Environmentalists warned of the ecological “catastrophe” after thousands of gallons of oil spilled into the protected Sundarbans mangrove area when a tanker collided with another vessel on Tuesday.

The area gives a home to rare Irrawaddy and Ganges dolphins and is listed by United Nations agency Unesco as a World Heritage site.

The tanker was carrying around 100,000 gallons of heating oil.

The government has sent a ship carrying oil dispersants to the area, but environmentalists warned that chemicals would harm the area’s delicate ecology.

The local port authority head said fishermen would use “sponges and sacks” to collect the spilled oil, which has already spread over a huge area.

Sundarbans chief forest official Amir Hosain said: “We’re worried about the long-term impact, because it happened in a fragile and sensitive ecosystem.”