India has reported cases of the Zika virus, the World Health Organization said, adding that efforts should be made to strengthen surveillance.

The WHO said that on May 15 India's health ministry reported three confirmed cases from the western state of Gujarat. Cases were detected during testing in February and November last year, while one was detected in January this year, according to the statement, which was released on Friday but did not gain public attention until Saturday.

A federal health ministry official said states were following standard protocols and there was "nothing to worry" about. The ministry had in March cited one confirmed case of Zika - from January of this year in Gujarat - while answering a question in India's parliament.