NEW DELHI: India's government, facing swelling protests over the gang-rape of a female student on a bus, vowed on Friday to press for life sentences for her six attackers and promised stricter policing.

Home Secretary R.K. Singh also said the government would pay the medical bills of the 23-year-old victim of the brutal Sunday night attack who is fighting for her life in hospital after suffering serious injuries to her intestines.

“We will ask for the maximum punishment of life imprisonment and ask the court for the speedy trial of the accused,” Singh said as New Delhi and other cities continued to be swept by an unprecedented wave of demonstrations by women demanding better safety.

Six drunken man were joyriding on a bus when they picked up the physiotherapy student and her 28-year-old male companion and took turns raping her. Afterwards, they threw the pair off the speeding vehicle.

Police say the woman was attacked with an iron rod after being raped.

Experts say a combination of abusive sexual behaviour, a scant fear of law and India's creaky judicial system encourages such attacks in the bustling city of 19 million people.

Five people, including the bus driver, have been arrested while a search is underway for the remaining suspect, city police commissioner Neeraj Kumar said.

Kumar said police have charged the detained suspects with rape and attempted murder.

“Police teams are close on the heels of the sixth and we will get him soon,” Kumar said at a joint news conference with the home secretary.

Kumar promised a slew of measures to “make Delhi safe,” promising squads of officers would patrol the city, crack down on vehicles with darkened windows and zero in on drunken motorists.

“All hooliganism will be swiftly punished,” the home secretary added.

The number of rape cases in New Delhi has risen 17 per cent to 661 this year compared with 2011. The number of rapes is triple the number reported in India's financial capital Mumbai.

Hundreds of people kept a vigil outside the hospital where the woman was being kept on life support after several rounds of surgery.

Kumar said police will deploy marshals on buses which are commonly used by women commuters.

“The (policing) regime that we are going to put in place will be very, very strict,” Kumar said, adding public transport drivers will be forced to carry identity tags.

If there is any wrongdoing “we will catch those people,” home secretary Singh added.

Singh also said the under-pressure government would take a “view” on the demands by protesters in several Indian cities for mandatory death sentences for rapists.

A parliamentary panel overseeing internal security said it would meet next week to review existing laws to deal with sex offenders.

The meeting will “deliberate on issues linked to incidents of rape”, panel chief Venkaiah Naidu told reporters.

New Delhi's metro system reserves a carriage in every train for women while several police stations in university districts have all-female staff to try and stem rising crime against women.