PHNOM PENH -- Actress Mia Farrow has been barred from holding a ceremony at a notorious Khmer Rouge prison as part of a campaign to pressure China to end abuses in Darfur, a Cambodian official said Wednesday.

The American actress has started an Olympic-style torch relay through countries that have suffered genocides to draw attention to China's close ties with Sudan, as Beijing prepares to host the Games in August.

The campaign aims to push Beijing to pressure Sudan into ending the violence in Darfur, where the United Nations estimates that at least 200,000 people have died in five years of war, famine and disease.

Her group, Dream for Darfur, had planned to hold a ceremony Sunday outside the Khmer Rouge's former prison, Tuol Sleng, which is now a genocide museum.

But interior ministry spokesman Khieu Sopheak said the event would not be allowed.

"The Olympic Games are not a political issue. Therefore, we won't allow any rally to light a torch," he told Agence France-Presse.

"We will not support the activity. We will not allow them to politicize the Olympic Games," he said, warning the group could face prosecution if they try to go ahead.

Farrow's group said the ceremony aimed to call attention to the constructive role that China could play in the Darfur crisis.

"The symbolic Olympic torch relay is urging the Chinese government, as both Olympic host and Sudan's strongest political and economic partner, to use its special influence with the Sudanese government," the group said in a statement.

In the run-up to the Beijing Olympics, China -- which is by far the largest foreign investor in Sudan and absorbs almost two-thirds of its oil output -- has been under mounting pressure to use its clout on Khartoum.

Cambodia would be the sixth stop for the group's relay, which began in Chad near the Sudanese border and continued to Rwanda, Armenia, Germany and Bosnia.