An investigating judge on the tribunal trying Khmer Rouge leaders in Cambodia has submitted his resignation complaining of government interference.

The tribunal issued a statement Monday saying international judge Siegfried Blunk tendered his resignation Saturday. It said he acted because public statements by government officials had called into question the integrity of two ongoing investigations.

Blunk – a German – already faced accusations that he and fellow investigating judge You Bunleng of Cambodia had given in to pressure not to pursue any cases beyond the two already brought to trial. The judges announced in April that they had completed their investigation of a third case, even though a prosecutor complained they had not questioned key witnesses or visited suspected crime scenes.

There are also accusations that the judges have not thoroughly investigated a fourth case presented by the prosecutors. Several tribunal staff members resigned earlier this year to protest the handling of the cases, and Human Rights Watch called last week for both investigating judges to resign.

The U.N.-backed tribunal has so far convicted one former Khmer Rouge prison warden and is trying the top four surviving Khmer Rouge leaders in a case that is expected to last for years.

In its statement Monday, the tribunal said senior government officials, including Prime Minister Hun Sen, have repeatedly argued that the tribunal should not pursue any more cases. It pointed out that Blunk initiated contempt of court proceedings against Cambodia's information minister over one such remark in May.

The most recent comment came last week from Cambodian Foreign Minister Hor Namhong, who said the decision on whether to pursue more cases must be made by Cambodians.

The tribunal said Blunk would not allow himself to be influenced by such statements, but that they cast doubt on his ability to perform his functions independently.

The tribunal was established to investigate and try suspected war crimes perpetrated during the period of Khmer Rouge rule in the late 1970s. The extreme communist group is blamed for the deaths of as many as 2 million people through executions, starvation and overwork.