LONDON, May 31, 2005 (AP) -- Rights and aid groups say the arrests of two officials from an international humanitarian group that spoke out about rapes in Darfur show how far the Sudanese government will go to keep news of atrocities off the world's front pages.

The foreign workers feeding, clothing and succoring the people of Darfur have an all too intimate view of the region's horrors. The Dutch branch of Medicins Sans Frontieres, for example, based much of its March report on rape on what doctors treating victims had seen and heard.

MSF said its doctors collected medical evidence of 500 rapes over 4 1/2 months, and that more than 80 percent of the victims reported that their attackers were soldiers or members of government-allied militia. The Sudanese government is accused of responding to a two-year-old rebellion in Darfur with a counterinsurgency campaign in which militiamen known as Janjaweed committed abuses _ including killings, rape and arson _ on such a scale that some have labeled what is happening there genocide.

Monday, the Medicins Sans Frontieres overall director for Sudan was charged with spreading false information and told not to leave the country pending trial. Tuesday, its Darfur coordinator was detained and brought to the capital.

Spokeswoman Susanne Staals said there are situations in which her group, also known as Doctors Without Borders, would confine itself to delivering aid and not also work to spread information. But MSF could not remain silent on Darfur "because the scale of the violence is immense and no action is being taken to protect victims," she said in a telephone interview from Amsterdam.

Leslie Lefkow, a Human Rights Watch researcher who has tracked developments in Darfur, said targeting Medicins San Frontieres was part of a pattern that included the arbitrary arrest and detention of or threats against more than 20 workers from several foreign agencies over the last six months.

Lefkow said aid workers and foreign journalists also were finding it increasingly difficult to get permission to visit Sudan, all part of what she called an attempt "to draw the veil over Darfur so that it drops off the international agenda."

Sudanese officials denied there was a campaign to interfere with aid agencies' work.

"There should not be any mixing of legal action taken against somebody and humanitarian action," Ahmed Adam, an official in Sudan's Ministry of Humanitarian Affairs, told The Associated Press on Tuesday. "Legal procedures here or anywhere in the world are no impediment to humanitarian work."

In Geneva, U.N. human rights chief Louise Arbour said Tuesday that targeting the humanitarian community for doing its work "will not only do a disservice to the people of Darfur; it will draw attention away from the real criminals, those who continue to rape, kill and pillage with impunity."

Journalists working in Darfur have found aid workers willing to talk about the atrocities they have witnessed and been told about, but often on condition of anonymity, not even allowing the names of their organizations to be used. They say they fear that if the Sudanese government knew who was speaking out, it would punish them by barring them from working in Darfur.

For months after the conflict broke out in early 2003, Sudanese officials severely limited international aid organizations' access to Darfur. Humanitarian workers were only allowed in after protracted negotiations and international pressure, and many feel their status remains precarious.