India on Friday executed four men convicted over the gang rape and murder of a woman on a New Delhi bus in December 2012 - a case that outraged a nation with one of the world's worst records for crimes against women.

Nationwide protests were held in the wake of the crime, forcing the government to frame tough anti-rape legislation.

Here is a timeline of the case:

December 16, 2012 - A 23-year-old physiotherapy student is brutally raped on a moving bus in the Indian capital of New Delhi. She and her male companion are tortured. A metal pipe is shoved into her abdomen, and her intestines are pulled out. They are thrown on the road side and left for dead.

Five men and a juvenile are arrested. Shocked by the brutality of the crime, large crowds gather for candlelit vigils in cities throughout the country, expressing outrage and praying for the victim as she clings to life.

December 29, 2012 - The victim dies in a hospital in Singapore after battling serious internal injuries. Protests erupt across India, calling out government indifference, gaps in law enforcement and rising sexual crimes against women.

January 17 2013 - A fast-track court begins proceedings against the five men and one juvenile in the case.

March 11, 2013 - Ram Singh, one of the main accused in the case and the driver of the bus, is found hanging in his prison cell.

April 2, 2013 - A tough new anti-rape law is passed, making stalking a crime and introducing the death sentence for convicted rapists.

September 2013 - The fast-track court sentences all four adult men to death in the case. The juvenile accused is remanded for a three-year term in a detention centre and is released in 2015, after serving his term.

May 5, 2017 - India's Supreme Court upholds the death penalty for the four remaining convicts. The men file review petitions challenging the order.

January 17, 2020 - Indian President Ram Nath Kovind rejects their pleas for mercy.

March 20, 2020 - The four men - gym instructor Vinay Sharma, bus cleaner Akshay Thakur, fruit seller Pawan Gupta and unemployed Mukesh Singh - are hanged at dawn in New Delhi's Tihar prison.