Several hundred Kenyan women have protested after a schoolgirl was brutally gang-raped and the only punishment for the suspects was that they had to mow the police station lawn.

The protesters marched on police headquarters in the Kenyan capital on Thursday to deliver a petition of over a million names demanding justice and decrying lack of action against those who carried out the rape.

The teenager, a 16-year-old girl publicly identified as Liz, was reportedly attacked, beaten and then raped by six men as she returned from her grandfather's funeral in western Kenya in June, before the gang dumped her, bleeding and unconscious, in a deep sewage ditch.

The online activist group Avaaz says Liz was gang-raped in June and she is now wheelchair-bound with a broken back, caused either by the beating or by being hurled down into the pit, and that she also suffered serious internal injuries from the rape.

The group says police arrested the suspected perpetrators but only made them cut grass at the police station as punishment.

Petition for prosecution

The lack of action has sparked outrage in the country. More than 1.3 million people have signed an Avaaz petition calling for the prosecution of the alleged rapists and an investigation of the police who freed the suspects.

Protesters marched through the streets of the Kenyan capital wearing T-shirts with the slogan "Justice for Liz", with activists draping dozens of women's knickers along the fence of the police station.

"What do we want? Respect, respect, respect, dignity!" they shouted.

"Slashing grass is not punishment for rape", a sign carried by a protester read.

Senior police officer William Thwere, who spoke to the organisers of the march, promised police were "investigating this issue... it will be dealt with the seriousness it deserves."

Rape is a major problem in Kenya, and is often not taken seriously by the police, according to studies.

One government study in 2009 found that as many as a fifth of women and girls were victims of sexual violence, although other later studies have put the rate even higher.

Another UN-backed government study in 2010 focusing on children found a third of girls and a fifth of boys had suffered sexual violence.

Source: Agencies