The toll from Hurricane Matthew crossed 1,000 in the island nation of Haiti, Reuters reported. Government officials said they had started burying the dead in mass graves after the Caribbean’s most devasting storm in a decade ripped through large parts of the country’s southwest.

The news agency reported that the official tally remains at 336 as officials are still reaching remote villages and updating their records. The Reuters tally was made by combining reports from the mayors of various towns in the country, as well as officials from other regions.

Three days of national mourning has been declared, with people offering prayers outside the ruins of church buildings, BBC reported. A United Nations humanitarian co-ordinator Mourad Wahba, said close to a million people are in “urgent need of humanitarian assistance”. Thousands of buildings, including major hospitals, have been destroyed and the country’s agricultural lands have been flattened, causing food security concerns.

Fears of a cholera outbreak are growing after at least 13 people died of the disease in various parts of the country. The communicable illness had left hundreds dead in Haiti in 2010 after it was struck by an earthquake.

Aid has been coming in from neighbouring countries such as the United States, where 16 people have been killed by the storm. The Red Cross has pledged millions of dollars.