Tightening the screws on a gang that allegedly sexually harassed and blackmailed a 19-year-old woman in Coimbatore district, police Tuesday booked four accused under the Goondas Act even as the Tamil Nadu government decided to handover the case to the CBI.

The case assumed political overtones after a local functionary of ruling AIADMK allegedly attacked the victim's brother and drew outrage with opposition parties led by DMK latching on to it ahead of the Lok Sabha elections.

The AIADMK subsequently expelled the functionary who had been arrested in the attack case.

In an apparent move to take the wind out of DMK's sails after the party targeted the AIADMK asking if it was protecting the accused, the state government decided to order a CBI probe into the case, hours after it was shifted to the Crime Branch CID from local police.

The harassment drew widespread condemnation after a leaked video of the survivor, in which she could be heard screaming and resisting her assailants.

The four men had on February 12 allegedly tried to strip the woman inside a car near Pollachi, over 500 km from here, and had shot a video of the act and blackmailed her using the visuals.

Reports in a section of media which claimed that the same gang had molested and blackmailed several other women, prompted political parties to demand a through probe and tough punishment for the accused.

A top state police official told PTI that the government has decided to transfer the case to the CBI and the administrative process of sending a formal request to the Centre was on.

Coimbatore District Collector Rajamani ordered detention of the four accused in the harassment case under the Goondas Act following recommendations by Superintendent of Police R Pandiarajan.

The four -- Thirunavakkarasu, Sathish, Sabariraj and Vasanthkumar- already under judicial custody had been booked under various sections of the IPC and Tamil Nadu Prohibition of Harassment of Women Act.

They will now face the Goondas Act as well which authorises detention upto a year.

Seeking to up the ante on the issue, the DMK led a demonstration at Pollachi.

Led by its Rajya Sabha MP Kanimozhi, the outfit's cadres, including women, demanded tough action in the case.

Some women raised slogans like "Render justice," and "Where is our security?"

Addressing the cadres, Kanimozhi said the case and violence against the victim has brought shame and demanded action.

She alleged the same network of criminals who had harassed the woman were involved in molesting over 250 women in the past seven years.

Kanimozhi lauded the victim's courage in freeing herself from the gang and later lodging a complaint.

Actor-politician Kamal Haasan met with Director General of Police T K Rajendran in Chennai and sought his intervention to ensure justice for the victim.

Haasan's party, Makkal Needhi Maiam, also took out a procession in Pollachi Tuesday demanding justice and tough action against the perpetrators.

The Communist Party of India and Amma Makkal Munnetra Kazhagam have also sought justice for the victim.

According to police, the woman who managed to free herself lodged a complaint on February 24.

Subsequently, the victim's brother was assaulted by members of the gang and AIADMK's local level functionary was also allegedly involved in it.

Four men, including the functionary, were arrested separately for the assault on the woman's brother, police said.

DMK President M K Stalin Monday hit out at the government asking if the AIADMK was protecting the accused.

"Why has there been no prompt action in the issue despite media unearthing the incident and protests held by DMK and other opposition parties?" he asked.

Leaders of other parties had also reacted sharply demanding justice.

On Monday, senior AIADMK leader Pollachi V Jayaraman had asserted it was his party that had been demanding tough action against the accused right from day one when the harassment came to light.

After the political reaction and the emergence of a leaked video, the AIADMK expelled the functionary, a ward secretary from the primary membership of the party on Monday.

Meanwhile, CPI State secretary Mutharasan alleged people suspected that some from the ruling party were supportive of the accused.

Amma Makkal Munnetra Kazhagam chief TTV Dhinakaran demanded a court monitored CBI probe to ensure justice.

The Democratic Youth Federation of India too demanded a court monitored probe and speedy action.

Meanwhile, the brother of the woman and some relatives requested the political parties not to politicise the issue, since it would prevent other victims to approach for justice.

The relatives, who had submitted a memorandum to the district collector with regard to the case, said such agitations by the political parties added to the stress already being felt by the girls and their parents.

An advocate, representing the victim, said police have arrested the people identified in their complaint.

"We are looking forward to further action," he said.

He wondered why some political parties were seeking the "arrest of the accused," when they had already been arrested and placed under judicial custody.