"The National Environment Agency is urging the public to wage an all-out war on the Aedes mosquito, which causes dengue fever," an agency statement said.

It said the disease, which typically strikes during the annual rainy seasons in Singapore and neighbouring Indonesia, Malaysia, Thailand and Vietnam, hit with unusual ferocity in the last three months of 2004 and worsened in January.

The monthly average for the October to January period, at 1,113, was nearly three times the average in the same quarter in 2003 and 2002, an agency spokeswoman said on Saturday.

More than 600 people died in Indonesia from dengue fever in the first four months of 2004 during its last rainy season, which runs from October to April, and health officials fear more deaths this year after the Indian Ocean tsunami.

Pools of stagnant water, a common sight in tsunami-ravaged regions such as Indonesia's Aceh province, are ideal breeding grounds for the Aedes mosquito. Relief workers have been spraying pesticides to hold down mosquito populations and prevent dengue.

In Singapore, January alone saw 1,145 cases, nearly four times the January average in the past three years. "Traditionally in Singapore, the number of cases will be lower in the October to March period," said the spokeswoman. "This is unusual".

Dengue fever usually strikes the island hardest during the warmer months of July to September.

Singapore's National Environment Agency added that the Indonesia capital of Jakarta saw about 18,000 cases of dengue fever last year, according to media reports compiled by the agency, while Malaysia had 33,203 suspected cases.

In December, Singapore sent out teams of volunteers to scour housing estates and parks to eliminate mosquito breeding sites, especially plant pots with standing water, in a project dubbed "mozzie attack"