A 20-year-old woman was allegedly gang raped by four men at knifepoint in the south Indian district of Kancheepuram in Tamil Nadu state, after they beat up her boyfriend.

The incident happened on Monday (9 October) night when the woman and her boyfriend, both of whom work in a textile shop in the area, were sitting under a tree after work hours. Police said the duo often used to go there to sit under the tree in order to spend some time together.

However, on Monday, four goons were already present there and started to misbehave with the couple. First, they thrashed the woman's friend and then took turns to rape her while one of them held a knife on the man, The Times of India reported.

The ordeal went on for at least three hours before the accused fled the scene, police said.

According to reports, the couple lodged a police complaint on Wednesday (11 October). The police then acted quickly to arrest three of the four suspects. "We narrowed down on the suspects after a few inquiries in the neighbourhood where some residents noticed them leaving in a hurry on their bikes," a police officer said.

He added that, during interrogation, the trio admitted that they were drunk and decided to assault the couple, threatening them with a knife.

Police are still on the lookout for the fourth suspect and have sent the woman to a government hospital for a medical examination.