The age of protesters ranged from 19 to 67
Up to 20 Britons who travelled to Iraq to form a human shield against military action are returning home amid safety fears.
The anti-war campaigners are on their way back to London in the double-decker buses which took them to Baghdad last month.
About 12 other Britons will stay on as part of the 200-strong international Truth Justice Peace Human Shield Action Group.
Their role is now to "protect" humanitarian sites and act as witnesses to the war, rather than as human shields.
Gordon Sloan, who is part of the international group remaining in Baghdad, told BBC News that four vehicles left on Sunday morning, carrying between 16 and 20 people.
We don't have the numbers in Baghdad to be an effective deterrent to stop the war
He said some of the people who left were frustrated by the Iraqi authorities dictating which sites they could be deployed to.
They were being prevented from going to hospitals and were being directed to sites they had not approved, he said.
The group would now try to protect UN-approved water and power supply locations which should not be under attack, Mr Sloan added.
"We do not have thousands of people here, we have hundreds, so now it's more about protecting sites, not stopping the war," he explained.
Christiaan Briggs, a coordinator for the action group in Baghdad, said those returning had always planned to do so before any bombing started.
He said: "The aim was always a mass migration and if we had had five to ten thousand people here, there would never be a war."
'Prepared to die'
On 17 February, a multinational group of 75 people arrived in the Iraqi capital, after the marathon 3,000-mile bus journey from London.
It was led by former US marine
and Gulf War veteran Ken Nichols O'Keefe.
A few days later, about 100 other protesters arrived from Heathrow to join them.
Mr Briggs said about a dozen Britons were still in Baghdad and that they may now concentrate on acting as witnesses to any military action.
Explaining the group's change of heart on the original human shield aim he said: "I said right from the start, I was prepared to die but when I knew I had a chance of effecting change."