The eight day long annual festival is observed to worship the god Devraj Indra, the lord of rain and good harvest.
It also marks end of monsoon and beginning of harvest season and festivity.
The chariot procession and mask dances are the main attraction of Indra Jatra.
On fourth day of festival the chariot procession of living Goddess Kumari, Lord Ganesha and Lord Bhairav began from historic Basantapur Durbar Square on Monday.
Nepal’s living Goddess Trishna Shakya made her first public appearance after she was anointed in September last year.
President Bidya Devi Bhandari and thousands of people attended the Indra Jatra celebrations.
The fesitval was started on Friday with erection of a sacred wooden pole (lingo) at Hanumandhoka in Basantapur Durbar Square. Indra Jatra is mainly celebrated by the Newar community of Kathmandu valley and some other parts of the country.
According to legend once upon a time Lord Indra disguised as a common man descended to the earth in search of a Parijat flower (a night flowering jasmine) to perform worship for his mother. The people caught him and tied while he was plucking the flowers. His mother came to Kathmandu in search of him.
When the city folk realized that they had captured Lord Indra they were appalled and immediately released him. After the release of Lord Indra, his mother promised to provide enough dew throughout the winter to ensure a rich crop.
It is believed that Kathmandu starts experiencing foggy mornings from Indra Jatra festival.