Wildlife officials say that previous counts were probably inaccurate, because some tigers were missed out and others were counted twice as they crossed from one country to the other.

It will be the world's largest census of tigers in a single geographical area.

Covering more than 10,000 square kilometres, the Sunderbans is home to an estimated 600 Royal Bengal Tigers.

At the last count last year, the Indian side of the forest contained 271 of the animals.

There has been no such count in Bangladesh in recent years.

"Tigers do not know political borders, but the Sunderbans is divided between two countries," Atanu Raha, chief conservator of forests in India's West Bengal state, told Reuters.

"So, we need a cross-border census to ensure there is more accurate counting as it is one single ecosystem."

Falling numbers

Poaching and illegal logging have affected the tigers' habitat in the mangrove forest, reducing their number in Bangladesh in the past few years.

Locals fear attacks from the tigers

This is despite reports that some of the tigers from the Indian side have migrated to Bangladesh during this period.

The UN-funded project will involve not only the counting of Royal Bengal Tigers, but also a study of their breeding and feeding behaviour.

Tigers kill nearly 50 people every year in the Indian Sunderbans alone.

It is hoped that the census may reveal why some tigers have become man-eaters.

"Human beings are not a natural diet for tigers," Mr Raha said.