Hundreds of people gathered in Phnom Penh yesterday to mark the International Day to End Impunity, calling on the government to tackle the issue by reforming its court system.

Speaking at the event at the capital's Cambodiana Hotel, Preap Kol, executive director of Transparency International Cambodia, said that impunity has become the "root cause" of social injustice in the Kingdom.

Kol called for a "systematic reformation", especially within the courts.

Cambodia's court system has come under fire in recent days following a raft of arrests, charges and convictions of land activists, monks and members of the opposition Cambodia National Rescue Party.

Rights groups have widely condemned the action, which seems to have been taken in spite of a lack of evidence.

Hundreds of people gathered for the second Sunday in a row yesterday outside of Prey Sar prison, where the detainees are being held, to demand their release.

In a speech last week, Prime Minister Hun Sen defended the judiciary and said the incarceration of the group was out of his hands.

Ith Rady, an undersecretary of state at the Ministry of Justice, yesterday reiterated the premier's claims that Cambodia's court system works effectively.

But NGOs once again hit out at the Kingdom's "flawed and protracted judicial process".

In a statement released yesterday, 16 NGOs called on the authorities to drop charges against a well-known activist monk, Venerable Luon Sovath, who is scheduled to face trial on Tuesday alongside members of the so-called "terrorist" Khmer People Power Movement (KPPM) on charges of treason and obstructing electoral procedures.

The statement says the planned trial goes against a judge's orders in 2012 that Sovath's case be separated from the case against KPPM leader Sourn Serey Ratha.

"The fact that a judicial order issued by the court has been completely ignored in a case involving such a well-known and respected human rights defender ... will continue to erode any confidence in the judicial system," said Brad Adams, executive director of Human Rights Watch's Asia Division.

Sovath said yesterday that he did not trust the court to give him a fair trial.

ADDITIONAL REPORTING BY ALICE CUDDY