DHAKA (Reuters) - The United Nations said the humanitarian crisis caused by last month's cyclone in Bangladesh was much worse than previously thought, with more than two million people in need of immediate life-saving assistance.

"As more information becomes available, an even grimmer reality is being revealed," the United Nations Office for the Coordination of Humanitarian Affairs said in a statement released in Dhaka on Tuesday.

About 2.6 million Bangladeshis across nine districts needed emergency assistance, and the total number of people affected by the cyclone was around 8.5 million, 1.5 million more than initially thought, the statement said.

Cyclone Sidr hit the impoverished South Asian country on November 15 with winds of 155 mph (250 kph) and a 5-foot tidal surge.

The confirmed death toll has increased slightly to 3,268, the number of people considered missing is 872 and the number of injured has been revised upward by 5,000 to nearly 40,000. Damage to property is also more severe than first reported. Nearly 564,000 homes have been completely destroyed, 200,000 more than initially estimated, the U.N. statement said. Another 885,280 houses have been damaged.

The United Nations said livestock losses numbered at least 1.25 million, more than double an initial estimate, and the estimated area of cropland damaged had risen to 2 million acres.

Food, shelter and cash were the three greatest needs in terms of emergency assistance, the United Nations said, but sanitation, drinking water, electricity and livelihood assistance are also critical.

So far the U.N. Central Emergency Response Fund has disbursed $14.7 million for relief efforts in the worst affected areas of Bangladesh, while international donors have contributed more than $143 million.

"As assessments are ongoing, additional funds might be required in order to provide comprehensive humanitarian assistance to populations affected by the storm, especially as new needs continue to be identified," the statement said.

Bangladesh has asked the international community for $1 billion to rebuild the impoverished country's southwestern coastal areas.

"As many as eight million face the bleak prospect of destitution," Fakhruddin Ahmed, the head of Bangladesh's interim government, told donors, adding that his government had mobilized all possible resources to help those in need.

(Reporting by Ruma Paul; Writing by Anis Ahmed, editing by Rosalind Russell)