NEW DELHI (AFP) - Police in India charged 18 people on Sunday after a frenzied mob stormed a prison and lynched a man accused of rape in the country's northeast, as tensions remained high, a senior officer said.

Police arrested the men for rioting in Nagaland state, but it was unclear if they were directly involved in killing Syed Farid Khan, whose body was then strung up to a clock tower on Thursday.

He had been accused of raping a 19-year-old tribal woman multiple times.

"So far we have arrested 18 people for rioting and unlawful assembly," the Inspector General of Police, Wabang Jamir, told AFP.

"We are now verifying if besides being part of the mob they were also directly involved in the lynching," Jamir said by phone from Dimapur city.

"We have already identified many more people (for arrest) from videos and photos (of the incident on social media)," he added.

Several thousand people overpowered security at the Dimapur Central Prison searching for Khan, whom the mob also believed was an illegal immigrant from Bangladesh.

The Bengali-speaking Khan was stripped and paraded on the streets outside, while men armed with sticks beat him to death, according to local media.

Hundreds of riot police have been patrolling the streets of Dimapur district since the incident, while Jamir said a curfew remained in place along with mobile phone and internet restrictions.

Tensions have been rising in Dimapur since Khan was arrested on February 24 for the alleged rape.

The lynching comes as India is in the midst of a raging controversy over a government order to ban the broadcast of a documentary about the December 2012 fatal gang-rape of a young student in New Delhi.

India has seen an outpouring of anger over frightening levels of violence against women since the 2012 attack, which sparked shock both within India and around the world.

But the lynching is also linked to ethnic tensions within Nagaland, whose indigenous groups have for years accused growing numbers migrants from Bangladesh of illegally settling on their land and eating into resources.

Khan's brother, who lives in neighbouring Assam state, on Saturday accused police of falsely implicating his brother in the rape to try to root out non-tribals from Nagaland.

The woman, who cannot be named for legal reasons, said Khan had given her 5,000 (S$110) rupees after the attack in return for her silence.

"It was only after the incident, he gave me the money to keep silent, so I took the money and gave it to the police station," the woman told the NDTV network.

Jamir said the women's initial medical report "confirmed rape and other ... injuries on her body".