The United Nations estimates the world population will reach 8 billion people on Tuesday, with the highest growth taking place in India and African nations.

The world population has increased by about 1 billion people in the past 12 years due to longer average life expectancies and declining mortality rates for mothers and children.

The UN says some South Asian countries and Africa will likely continue to see substantial increases in population.

India is projected to surpass China as the world's most populous country in 2023.

Countries in sub-Saharan Africa are expected to account for more than half of the global population increase anticipated through 2050.

The UN also says the population of 61 countries or areas, including Japan, are projected to decrease by 1 percent or more by 2050 partly due to sustained low fertility levels.

The global population is projected to peak at around 10.4 billion people in the 2080s and then decline.

The UN Department of Economic and Social Affairs says countries where fertility levels remain high should prepare to meet the needs of growing numbers of children, such as providing them with quality education and employment opportunities.

The UN department also says countries with aging populations should take steps to adapt public programs to the growing proportion of older persons.