A group of about 60 failed Iraqi asylum seekers have been forcibly deported from several EU countries to Baghdad.
The move sparked anger from human rights and refugee groups who believe the situation in Iraq is too dangerous for them to return.
It is thought the flight carrying the Iraqi nationals left Britain early on Wednesday morning, stopping in Sweden on the way, before landing in the Iraqi capital.
Thirty of the Iraqi nationals are believed to have come from Denmark, Britain and the Netherlands, with another 28 from Sweden.
Peter Kessler, a spokesman for the United Nations High Commissioner for Refugees (UNHCR), said individuals could face acts of violence and human rights abuse on return to the country, which is still experiencing suicide bombings and sectarian attacks.
In a statement, Sweden's border police department said: "Seats aboard the chartered plane have been offered to other police forces in Sweden and EU member states through Frontex, the agency responsible for co-ordinating return operations.
"A number of these seats have already been booked. Sweden is the organising state and each country is responsible for its returnees".
'Lives at risk'
"We are asking the government to continue hosting people from central Iraq until such a time that they can be returned in safety," Kessler said.
"The situation in central Iraq is very unstable due to the prevailing violence, security incidents and human rights violations going on. Their lives could be at risk."
"Until the situation improves and it is safe to return to Iraq, these people should be offered some form of protection in the UK"
Carolyn Ennis, a senior protection officer from the UNHCR, told Al Jazeera that people "should only return voluntarily in the current situation".
"There's a gradual trend of increasing voluntary returns to Iraq. We would hope that the situation will improve with the installation of a new government," she said.
"Individuals who say they are not safe [in Iraq], in our opinion, should not be forced to return."
Amnesty International also condemned the move, saying it was "unfathomable that the UK can consider Baghdad a safe place to return people".
"Our report in April documented scores of civilian killings, some of whom were tortured and their bodies mutilated before they were dumped in the street," Jan Shaw, Amnesty's UK refugee programme director, said.
"Until the situation improves and it is safe to return to Iraq, these people should be offered some form of protection in the UK."
David Cameron, the British prime minister, defended the move, saying that UK troops had fought to ensure the country was safe enough for refugees to return.
"Iraq now at least has some chance of stability and of democracy and we're actually seeing some progress in Iraq," he told politicians on Wednesday.
"One of the reasons that our brave servicemen and women fought and died in Iraq was to try to make that a more stable country and a country that people who had fled would be able to return to."
Another 50 people are expected to be forcibly deported next Wednesday, Dashty Jamal of the International Federation of Iraqi Refugees told the AFP news agency.
"The UK is responsible for their lives. If anything happens, the UK government is responsible," he said.
The UK Border Agency has said the security situation in Iraq is "signficantly better now than it was in 2008," when courts first said it was possible to return people to Iraq following the 2003 invasion.
"Since October 2009 we have been working closely with the government of Iraq to agree on the return of Iraqi citizens not in need of protection, who are eligible for removal from the UK," Matthew Coats, head of immigration at the agency said.
"This approach is in line with how other EU member states regularly arrange returns to Iraq."
Last year, the UK forcibly deported 44 failed Iraqi asylum seekers to Baghdad, but only 10 were allowed to enter and the rest were flown back to Britain.
Separate deportations to the Kurdish north of Iraq have also taken place.