Thousands of diaspora Indians protested in more than 130 cities across 25 countries on Sunday, organisers said, to demand justice after last month's rape and murder of a trainee doctor at a hospital in the city of Kolkata.

The protests started in large and small groups across Japan, Australia, Taiwan and Singapore, before spreading to cities in Europe and the U.S.

They added to ongoing nationwide protests in India after the Aug. 9 killing of the 31-year-old postgraduate student of chest medicine. A suspect has been arrested along with the former principal of R.G. Kar Medical College where the victim was studying.

"The news of this heinous crime committed on a young trainee doctor while on duty numbed and shocked each of us at the sheer ruthlessness, brutality and disregard of human life," said Dipti Jain, an organiser of the global protests.

The doctor had retired to sleep on a piece of carpet in a seminar room after a marathon 36-hour shift, given the lack of dorms or resting rooms. She was later found bleeding from her eyes and mouth, with injuries to her legs, stomach, ankles, her right hand and finger, according to a doctor's inquest report accessed by Reuters.

Hundreds of protesters gathered in several cities in the San Francisco Bay Area, demanding accountability for the crime and safety for Indian women.

In Dublin, California, about 35 miles (56 km) east of San Francisco, protesters formed a human chain, shouting slogans and waving placards that read "We demand justice" and "Shout it loud, shout it far, justice for R.G. Kar".

People across ages, including young children and seniors, recited poems and took part in a street theatre.

"While we do want women's safety, this is about the safety of everyone at their workplaces," said Sukalpa Chowdhury, a 39-year-old physician who joined the protests in Dublin.

"How can we have our future generations, who will go to the same institutes, feel safe, get a good education and serve society? That is a big concern for everyone."

At another protest in the Swedish capital Stockholm, scores of mainly black-clad women gathered in Sergels Torg square to sing songs in Bengali and hold signs.

Although tougher laws were introduced after the 2012 gruesome gang rape and murder of a 23-year-old student on a moving bus in New Delhi, activists say the Kolkata case shows how women continue to suffer from sexual violence.

India's federal police are investigating the crime but are yet to file charges. The country's Supreme Court created a hospital safety task force last month to recommend steps to ensure medical workers' safety.