As populations grow and land becomes scarcer, attacks on those trying to defend their land are becoming increasingly frequent, a top rights group warned Tuesday, citing Latin America and Asia as the main problem areas.

In a wide-ranging report covering 29 countries, the International Federation of Human Rights (FIDH) said that "land rights defenders have never before been so targeted."

"Pressure on land has today become unsustainable, and demanding that a community's economic, social and cultural rights are respected has become a high-risk activity," the FIDH said.

The group said that 43 land rights defenders had been murdered between 2011 and 2014 and 123 had been the victim of "judicial harassment".

These numbers are only "a small glimpse of the reality on the ground", it said. All regions in the world are concerned, Asia and Latin America being the continents most affected, the report noted.

People standing up for their land rights are often attacked by "police, military, private security agents or 'mercenaries'," the report claimed, in a bid to "silence opposition voices that might put a brake on an investment project."

"Threats, harassment, arbitrary arrest, assault, murder -- such acts are targeted at land rights defenders more than any other kind of human rights defender," the report concludes.

The detailed, 150-page report, published simultaneously in Manila, Pretoria, Mexico City and Guatemala, alleges cases of murders or disappearances in Mexico, Colombia, Honduras, Philippines, Thailand, Laos and South Africa.

At a lower level, the organisation spells out a host of cases of judicial "harassment" of people who often have little recourse to legal advice.

More than 95 percent of cases of legal harassment go unpunished, the FIDH report charged.

To resolve the problem, the group urged better international laws to protect those defending land rights and called for the issue to be put on the agenda of the 2015 international climate conference.

FIDH is an umbrella group representing 175 human rights organisations across the world with its secretariat based in Paris.