GENEVA (AFP) - An exiled Iranian opposition group on Friday urged the international community to help lift the "blockade" of a refugee camp near Baghdad and called for an investigation into killings at a second camp.

"We are asking for the United States and the UN to intervene to immediately lift the medicine and food blockade" of Camp Liberty, said Maryam Radjavi, who heads the France-based National Council of Resistance of Iran.

Camp Liberty, a former US military base, houses some 3,800 members of Iran's main opposition group, the People's Mujahedeen Organisation of Iran (PMOI).

Speaking on the sidelines of the UN Human Rights Council in Geneva, Radjavi also regretted the increased "harassment, intimidations and provocations by Iraqi security forces" of those inside the camp.

She told a conference that sick people were being blocked from visiting hospital and residents barred from bringing in building material to repair shelters damaged in a December rocket attack, which killed four people.

Washington, the EU and the UN should ask the UN Security Council to examine the situation in the camp "to avoid another humanitarian catastrophe," she insisted.

Jean Ziegler, a Swiss consultant to the Human Rights Council who also spoke at Friday's conference, said the blockade of Camp Liberty was "a war crime, because they are starving civilians".

"These people risk dying," he said, calling for UN observers and peacekeepers to be sent to the camp.

Many of Camp Liberty's residents were transferred from the PMOI's former Ashraf camp, which saw 52 people shot dead last September.

The Iraqi government blames the violence on PMOI in-fighting but the exiles attribute it to the Baghdad government, which they believe launched the assault at the demand of Tehran.

Radjavi on Friday reiterated PMOI's call for an "independent investigation" into the killings to prevent any "repetition of such crimes".

Scores of PMOI members have been killed in more than a dozen attacks on their camps since US troops withdrew from Iraq at the end of 2011.

The group was founded in the 1960s in opposition to Iran's Shah and later the country's clerical rulers.

It set up camp in Iraq during Saddam Hussein's war with Iran in the 1980s, but was disarmed after the US-led invasion of Iraq in 2003 toppled Hussein.

Today's Shia-majority and Iran-friendly government in Baghdad is eager to see it move elsewhere.