Indian officials are vowing to take measures to better protect women following the brutal gang rape of a 23-year-old student on a bus in the capital.

Police have so far arrested five people in connection with Sunday's attack and said Friday that they are searching for a sixth assailant. The suspects are accused of rape and attempted murder, with police seeking life imprisonment for the perpetrators.

The woman was attacked after she and a male friend were given a ride on a chartered bus in New Delhi. Officials say a group of men raped her and beat both of the victims with an iron rod, later stripping them and dumping them on the road. The woman remains hospitalized with severe internal injuries.

Indian Home Secretary R.K. Singh on Friday announced a series of measures to prevent such violence. He said bus drivers' licenses will be thoroughly checked, tinted or otherwise covered bus windows will be banned, and plainclothes police officers will be deployed on buses. Authorities will also crack down on drunk driving and those who drink and loiter in New Delhi.

Meanwhile, hundreds of protesters in the Indian capital marched to the presidential mansion on Friday, demanding strong action against those accused in the attack and better protection for women against violence and harassment.

More than 600 cases of rape have been reported in New Delhi so far this year, one of the highest rates in the country.

On Thursday, an Indian think tank released a study revealing that 27 political candidates have been accused of raping women. The Association for Democratic Reforms did not, however, record how many of the accused have been found guilty.