PHNOM PENH, Cambodia -- The fields of Choeung Ek on the outskirts of the Cambodian capital, Phnom Penh, carry a dark secret.

Across the baked earth scraps of cloth and human bone poke through the soil and are slowly bleached white by the harsh tropical sun.

In the center stands a glass-walled shrine containing more than 8,000 skulls -- the remains of just a few of those who died here.

These are the Killing Fields of Cambodia.

Here, just a few kilometers from the center of Phnom Penh, tens of thousands of people met their deaths -- entire families wiped out.

Many of those killed were intellectuals or trained professionals -- people considered counter-revolutionaries by the Khmer Rouge leadership bent on turning Cambodia into a peasant's paradise.

Towards the end of its rule, as the regime became increasingly paranoid and turned on itself, many once senior Khmer Rouge cadres also met their end at Choeung Ek.

Men, women and children -- some just a few months old -- were killed here, often in the most violent and brutal ways.

With bullets in short supply, the condemned were forced to kneel before an open grave then stabbed through the head with a sharpened bamboo stake.

Just one example of the horrors these now silent fields have witnessed.

Reign of terror
In the corner of the field stands a tree -- tall, flourishing and peaceful now. A fading sign next to it, accompanied by a rudimentary painting, betrays its terrible past.

Against its trunk the heads of babies were smashed by young men brainwashed into believing their actions would free Cambodia from colonial imperialism.

But Choeung Ek is far from unique.

The evidence of the Khmer Rouge's brutal reign of terror litters the Cambodian countryside.

More mass graves are being discovered all the time.

In all about 1.7 million people are thought to have died as a result of the regime's policies -- either through starvation, execution or sheer exhaustion.

Paranoia
Beginning with the forced evacuation of Cambodia's towns and cities the Khmer Rouge set about transforming the countryside into a massive system of collective farms.

Machinery was non-existent -- mass labor was seen as the way to overcome any obstacle.

Burdened by inefficiency and the ideological paranoia of their masters tens of thousands were worked to death -- others were executed for stealing just a few grains of rice to supplement their meager rations.

Behind it all was a group bearing the sinister title of 'Angkar', or The Organization, the preferred nom de guerre of the Khmer Rouge.

At its head was the so-called Brother Number One, the now infamous leader Pol Pot.

Yet for all the death and misery the Khmer Rouge wrought on this small Southeast Asian nation, no one has stood trial for the group's crimes.

Pol Pot died in his jungle hideaway in 1998, held under house arrest by a Khmer Rouge that had by then turned on its former leader.

Other former leaders have defected to the government in return for amnesty and now live a life of privilege mostly in the former Khmer Rouge stronghold of Pailin, in western Cambodia.

After years of debate and uncertainty the government says it is now willing to go ahead with bringing some members of the regime to trial -- who exactly that will be remains to be seen.

Only two leading members are currently in custody -- Ta Mok, the one legged Khmer Rouge military leader, known as "the Butcher"; and Kaing Khek Iev, or "Duch", the former chief executioner and head of the S-21 security prison, most of whose inmates ended their days in the fields of Choeung Ek.

How much longer they will remain in jail is unclear.

For many Cambodians the horrors of the past will never be fully laid to rest until those who brought about this country's suffering are brought to justice.