* Iraq security forces clashed with Iranian dissidents
* U.S. Senator Kerry: Iraq must investigate the "massacre"
* Iranian dissident leader calls for U.N. monitors at camp (Adds Senator Kerry reaction, background; paragraphs 6-8, 11)
By Louis Charbonneau
UNITED NATIONS, April 14 (Reuters) - The United Nations on Thursday confirmed 34 people have been found dead at an Iranian dissident camp in Iraq after Iraqi security forces moved against the camp last week.
"We are aware of 34 dead in the camp and its immediate environs," U.N. spokesman Farhan Haq said. "We're trying to get further details."
He said U.N. officials visited the camp on Wednesday.
The fatality count was the same number of deaths Camp Ashraf residents had reported. Their death toll was disputed by Iraqi authorities, who said only three people were killed in the operation and others were dead before troops moved in.
Iraqi authorities say the three were killed when security forces responded to rock-throwing and threats by residents during an operation to reclaim land from the camp and return it to farmers. The Iraqi Defense Ministry has said it will launch an investigation into the operation. [ID:nLDE73B0P0]
U.S. Senator John Kerry, chairman of the Senate Foreign Relations Committee, said the U.N. confirmation was "deeply disturbing and the Iraqi military action is simply unacceptable."
He said in a statement that the situation at the camp was untenable and urged the Iraqis to take "corrective action" and "stop the bleeding."
"The Iraqi government has announced a full investigation into the massacre and it must be thorough and serious," he said. "The investigation must hold accountable the responsible parties and ensure that there will be no sequel."
Ashraf is the base of the People's Mujahideen Organization of Iran, which the United States, Iraq and Iran consider a terrorist organization, although the European Union removed it from its terrorism blacklist in 2009.
The group, seeking the overthrow of Iran's Islamic government, mounted attacks on Iran from Iraq before Saddam Hussein's 2003 downfall. In the 1970s, it led a guerrilla campaign against the U.S.-backed Shah of Iran, including attacks on U.S. targets.
Hussein gave it refuge in Iraq in the 1980s and some of its fighters joined him in the 1980-1988 war against Iran. The group surrendered its weapons to U.S. forces after the 2003 invasion that ousted Saddam.
Maryam Rajavi, head of the group's political wing, the National Council of Resistance of Iran, said the U.N. statement confirmed "the scope of the crimes perpetrated by the Iraqi forces ... against defenseless and civilian Ashraf residents."
"This atrocity is a clear case of crime against humanity, war crime and crime against (the) international community," she said in a statement, adding that a U.N. team should remain at Camp Ashraf to monitor the situation there. (Reporting by Louis Charbonneau; editing by Mohammad Zargham)