The Mexican authorities must act to halt the continuing abuse of migrants who are preyed on by criminal gangs while public officials turn a blind eye or even play an active part in kidnappings, rapes and murders, Amnesty International said in a new report released on Tuesday.

Invisible Victims: Migrants on the Move in Mexico, documents the alarming levels of abuse faced by the tens of thousands of Central American irregular migrants that every year attempt to reach the US by crossing Mexico.

"Migrants in Mexico are facing a major human rights crisis leaving them with virtually no access to justice, fearing reprisals and deportation if they complain of abuses," said Rupert Knox, Mexico Researcher at Amnesty International.

"Persistent failure by the authorities to tackle abuses carried out against irregular migrants has made their journey through Mexico one of the most dangerous in the world."

Kidnappings of migrants, mainly for ransom, reached new heights in 2009, with the National Human Rights Commission (CNDH) reporting that nearly 10,000 were abducted over six months and almost half of interviewed victims saying that public officials were involved in their kidnapping.

An estimated six out of 10 migrant women and girls experience sexual violence, allegedly prompting some people smugglers to demand that women receive contraceptive injections ahead of the journey, to avoid them falling pregnant as a result of rape.

On 23 January 2010, armed police stopped a freight train carrying over 100 migrants in Chiapas State, southern Mexico.

Veronica (not her real name) said that Federal Police forced her and the other migrants to leave the train and lie face down on the ground, before stealing their belongings and threatening to kill them unless they continued their journey by foot along the railway.

After walking for hours, the group was assaulted by armed men who raped Veronica and killed at least one other migrant.

Two suspects were later detained after a local activist helped the migrants file a complaint but no action was taken against the Federal Police, despite migrants identifying two officers allegedly involved.

"Mexico has a responsibility to prevent, punish and remedy abuses whether these are committed by criminal gangs or public officials," said Rupert Knox.