The World Health Organization (WHO) has classified the coronavirus variant first found in India last year as a "variant of global concern".
It said preliminary studies show the B.1.617 mutation spreads more easily than other variants and requires further study.
The variant has already spread to more than 30 countries, the WHO says.
Three other variants from the UK, South Africa and Brazil have been given the same designation.
A mutation is elevated from a "variant of interest" to a "variant of concern" (VOC) when it shows evidence of fulfilling at least one of several criteria, including easy transmission, more severe illness, reduced neutralisation by antibodies or reduced effectiveness of treatment and vaccines.