GENEVA, Aug 5 (Reuters) - Iraqi authorities are blocking supplies of food and water going into a camp east of Baghdad where Iranian exiles have been living for over 20 years, Swiss- based human rights activists said on Wednesday.

The activists, including senior U.N. expert Jean Ziegler, said they feared a repetition of what they called a brutal attack on the camp by Iraqi special forces on July 28 when at least 7 residents died and many others were injured.

"Preventing people getting food is a gross violation of international law ... This has been going on for 10 days. It is totally scandalous," Ziegler, a top adviser to the U.N. Human Rights Council, told a news conference.

Eric Sottas, General Secretary of the Geneva-based World Organisation against Torture (OMCT), deplored what he called "a sort of passivity on the part of international bodies" over events around the camp, home to some 3,500 people.

"Unless these unarmed and defenceless people are properly protected, this could happen again, perhaps worse," he said.

The two called on the International Committee of the Red Cross (ICRC) to establish a presence in Ashraf, which houses members of the anti-Tehran People's Mujahideen Organisation of Iran (PMOI) and their families.

Asked later about their appeal, ICRC President Jakob Kellenberger told Reuters the humanitarian body "will always speak in favour of humane treatment and of respect of the existing law." It had sent a team to inspect Ashraf recently.

Ziegler and Sottas urged U.S. forces, which as part of Washington's withdrawal strategy have handed responsibility for the camp to the Iraqi government, to resume its security role there pending the dispatch of a United Nations force.

Camp residents say 13 people were killed when the Iraqis moved in, while 36 were seized. Iraqi police say these are under investigation for rioting but the exiles say they fear they will be handed over to Iran to face torture and death.

The Iraqi government says the July 28 action -- which has been fiercely criticised by other global human rights groups including Amnesty International -- was undertaken to establish control following the U.S. pull-back.

The news conference, called by the OMCT and also attended by Europe-based representatives of the PMOI and by mothers of men in the camp, was shown what Sottas said was film of the Iraqi operation with scenes of violence against the inmates.

It showed an armoured vehicle drive into crowds apparently inside the camp, zig-zagging from side to side and running several people down. Police were shown beating men and women with staves, while one officer brandished an axe.

Iraqi government spokesman Ali al-Dabbagh said last week that five of the seven the government acknowledges were killed threw themselves in front of police vehicles, while the other two were shot by PMOI snipers to stop them leaving the camp.