Several immigration centres across England and Scotland have been blockaded by human rights activists.
Three people chained themselves to a car near Bristol
The No Borders Network were campaigning against the use of dawn raids.
Offices in Portishead, near Bristol, Portsmouth, Newcastle and Glasgow were targeted by protesters over how failed asylum seekers are removed from the UK.
"We accept asylum can be an emotive issue and that people are entitled to peaceful protest," a Border and Immigration Agency spokesman said.
"However, failed asylum seekers who have no right to remain in the country and who do not leave will be removed.
"The government will take a robust approach to removing people from the country who have no legal right to be here.
"This is done in the most sensitive way possible, treating those to be removed with courtesy and dignity."
At the centre near Bristol, about 15 protesters blockaded the entrance to the offices with a car, with three people chaining themselves to it.
Protester Phillipa Brian, 27, said: "This morning we prevented a dawn raid just as a car was going out to take a family.
"We knew that if a dawn raid was going to happen, it would happen at this time and we got lucky."
Four people were arrested in Glasgow.