It was early in the morning when housewife Ngin Savoeun woke to cries for help from her neighbours. A survivor of Cambodia's Khmer Rouge regime – whose soldiers had murdered her husband in 1979 – she had not imagined she would hear such cries again in her lifetime.

Yet on that night in November, she heard the screams of neighbours as they rushed from their homes around the shore of Boeung Kak Lake, located in the heart of the country's capital, Phnom Penh.

And then she had to flee as well.

This time, however, her home was not under threat from Khmer Rouge guerrillas, but was instead demolished by armed construction workers, hired by a land development corporation to carry out one of the capital's most ambitious new property developments.

As part of this work, thousands of tonnes of mud and sand, scooped up from a nearby river, were being pumped directly into the homes of hundreds of local residents – often, the residents say, without warning. "They started pumping the water and sand in at night," says Tep Vanny, "while we were sleeping."

In this way, developers were attempting the complete removal of a 90-hectare historic lake from the heart of the capital and its replacement by a residential, commercial and entertainment district. About 20,000 people, many of whom have lived on the lake and around its edges for decades, are in danger of losing their homes.

According to the UN Special Rapporteur on Human Rights in Cambodia, Professor Surya P Subedi, this is "not an isolated case". It is "representative of the problems of this nature that exist in the country. Land grabbing by the rich and powerful is a major problem."

Cambodian civil rights group Adhoc says that last year alone, 12,389 families became the victims of forced evictions. Another rights group, housing advocates STT, estimates that around 10% of the population of Phnom Penh has faced eviction in the last decade.

At the same time, the Cambodian ministry of agriculture, forestry and fisheries says that the government granted more than 1.38m hectares of land in concessions to 142 different private companies between 1993 and June 2010.

Many of these evictions – including those at Boeung Kak – have taken place under the noses of international agencies.

Last month the World Bank announced the results of an internal inquiry into evictions that had taken place during a land-titling project involving the bank and the Cambodian government that ran from 2002 to 2009. The World Bank concluded in an official statement that the evictions at Boeung Kak had taken place "in violation of bank policy on involuntary resettlement" and "resulted in grave harm to the affected families and communities."

Residents had been "denied access to due process of adjudication of their property claims" and were displaced "in violation of policies the bank agreed with the government for handling resettlement", it said in the statement, calling on the Cambodian government to end the evictions.

Cambodia's ministry of land management countered that the Boeung Kak settlements had been outside the remit of the land-titling project, and were therefore "not under the conditions set for social safeguards".

"The problem goes back to the war," says Sung Bonna, chief executive officer of Bonna Realty Group and vice-president of the Cambodian Real Estate Development Association. "When the Khmer Rouge took over in 1975, they destroyed all the records of who owned what and made everything the property of the state."

The Khmer Rouge forcibly evacuated the population of Phnom Penh. Many Cambodians' homes were destroyed, while many people tried to settle away from the violence. Boeung Kak Lake was one such place.

In 2001, the government recognised the lack of land title and ruled that those who could prove more than five years of continuous, unchallenged occupancy of a property could apply to own it. Many Boeung Kak residents applied, but were denied title en masse, according to a January report on the issue from Bridges Across Borders Cambodia, an NGO advocating for the residents.

"In the same month, the Cambodian government entered into a 99-year lease agreement with private developer Shukaku Inc," the report also said. Representatives from Shukaku Inc declined to comment on the matter.

"The problems have all arisen first because of the war and second because of a lack of proper management of the changes," says Bonna. "But now, though, we have a much-improving situation and more or less soon, the problem will be no more."

Indeed, now only around a quarter of Boeung Kak Lake remains. "I spent three and a half years living in hell under the Khmer Rouge," said Ngin, surveying the half buried remains of her home of 32 years. "And now I am in hell again."