Several hundred Iranian exiles arrived at a UN-approved site near Baghdad on Saturday, a first step in a process that aims to see them resettled outside Iraq where they have been based for decades.

The move is part of a December 25 deal between the United Nations and Iraq, reached after extensive talks.

Under the deal, around 3,400 Iranians opposed to the Tehran regime are to move from their long-time base, Camp Ashraf, to a new location called Camp Liberty, with the aim of eventually being resettled in other countries.

"We are arriving at the gate to (Camp) Liberty," Behzad Saffari, the legal adviser for residents of Camp Ashraf, told AFP by telephone at around 6:00 am (0300 GMT).

The 397 exiles had departed Camp Ashraf in 18 buses from about 1:30 am on Saturday, escorted by Iraqi security forces, Saffari said.

Their arrival at Camp Liberty was not without problems, with Saffari saying the exiles objected to additional searches of their belongings, which had already been searched in a nearly 12-hour process before leaving Ashraf, though they eventually conceded.

Saffari also said Iraqi security forces wanted to assign the exiles housing within the camp, a move they also opposed, leading to more delays.

"We want to determine who goes where; it's not a prison here," he said.

It was not possible to independently verify the account, as journalists were not allowed to go to the camp.

Camp Liberty is a former US military base that once featured fast-food restaurants such as Burger King, Taco Bell and Subway. The exiles are to live in housing trailers of the kind once used by American soldiers here.

Iraq had aimed to close Camp Ashraf in Diyala province, which now-executed dictator Saddam Hussein allowed the People's Mujahedeen Organisation of Iran (PMOI) to set up during his 1980-1988 war with Iran, by the end of last year.

But Prime Minister Nuri al-Maliki said on December 21 his government had agreed to extend the deadline to April, and signed the deal with the United Nations on moving the exiles a few days later.

UN envoy to Iraq Martin Kobler was present when the exiles arrived at Camp Liberty and welcomed the move, a UN statement said.

"I commend the residents for their decision to move to Camp Hurriya (Liberty). This is the first step towards a better future outside Iraq. I look forward to their continued cooperation with the Iraqi authorities to complete the relocation without delay," it quoted him as saying.

Kobler said the UN would monitor the entire relocation process and provide round-the-clock human rights monitoring at Camp Liberty, and called on potential countries of asylum to confirm their readiness to admit the exiles, whose situation in Iraq has been a long-running sore.

The National Council of Resistance of Iran, an umbrella group that includes the PMOI, has complained about the conditions at Camp Liberty, and called for Iraqi police to be withdrawn before more exiles move there.

The left-wing PMOI was founded in the 1960s to oppose the shah of Iran, but took up arms against Iran's new clerical rulers after the Islamic revolution in 1979. It said in 2001 that it had renounced violence.

The US State Department has blacklisted it as a terrorist organisation since 1997, and says PMOI members carried out a large number of attacks over several decades against Iranian targets, and also against Americans.

The PMOI strongly opposes the terrorist designation and is seeking to have it lifted in the United States, as it has been in Europe.

In May 2005, Human Rights Watch (HRW) cited former PMOI members as having "reported abuses ranging from detention and persecution of ordinary members wishing to leave the organisation, to lengthy solitary confinements, severe beatings and torture of dissident members."

Despite PMOI objections, HRW has said it stands by its findings.

Camp Ashraf was disarmed following the 2003 US-led invasion of Iraq, which brought Iran-backed Shiites leaders to power in Baghdad, and came under US military protection.

But American forces transferred security responsibilities to Baghdad in January 2009.

Iraqi security forces raided Camp Ashraf in July 2009, leading to clashes in which 11 residents were said to have been killed and several hundred wounded.

A controversial April 2011 raid by Iraqi security forces left 36 people dead and scores injured.