The rapid spread of dengue in Delhi and Mumbai has forced the civic authorities to scramble into action to prevent an epidemic.

Mumbai has reported four suspected dengue deaths this week, a Brihanmumbai Municipal Corporation official said.

The cases reported from private hospitals, however, could not be confirmed, BMC's Deputy Executive Health Officer Dr J G Thanekar said.

The BMC has launched a drive to prevent breeding of dengue virus-carrying mosquitoes, officials said.

As compared to 135 cases last year, this year 160 have been reported till September with 70 cases in the month, Dr Thanekar said.

"The reason for the increase in number this time could be heavy rains throughout the season unlike last year," he added.

The tiger mosquito carries the dengue virus, and its symptoms are headache, high fever, chills and rashes.

The Indian capital has reported 618 cases, according to the Municipal Corporation of Delhi.

In Delhi, National Institute of Communicable Diseases officials blamed prolonged rain, absence of proper drainage and sanitation system as main causes for the spread of tiger mosquitoes.

"Every 5-6 years one or the other epidemic hits Delhi. This time it could be dengue, which so far has infected about 600 people in the capital," Delhi Medical Association president Dr Anil Bansal said.

The All India Institute of Medical Science said it has received 26 suspected dengue cases so far, out of which eight have been confirmed for the disease, its spokeswoman Dr Arti Vij said.

Three patients who were admitted in the institute for the treatment of the disease have been discharged, Dr Vij added.

Delhi Health Minister Dr A K Walia has issued directives to all blood banks and laboratories in all the hospitals in Delhi to remain functional round the clock.

Directives have also been issued to all the hospitals to keep reserve beds for dengue patients.