A group of residents from the Indian Ocean French islands of Mayotte has been rounding up suspected illegal migrants and taking them to local police, reports BBC News.
The move targeted around 100 "foreigners, Comorans and Africans", a member of the group told AFP.
Protests against the economic crisis and illegal immigrants from the Comoros islands have paralysed the island.
Mayotte, which voted to become part of France in 2009, has been in turmoil since mid-February.
France's minister for overseas territories, Annick Girardin, has condemned the move, saying "this kind of practice does not exist in a département".1
She urged the population to let the police do their job, adding that security arrangements were already in place.
Locals complain that the arrivals of migrants are putting Mayotte's health, housing and education services under pressure
About 70% of the 10,000 babies born every year in the island's only maternity hospital in the main town of Mamoudzou are born to illegal migrants, mainly from the Comoran islands, according to official statistics.
It is said to be one of France's busiest - to the point that the government is considering declaring the hospital as non-French territory so that children born there do not automatically qualify for French citizenship.
1: A département is a French administrative region that is equivalent to a county.
Read more of this report from BBC News.
See also:
'Just like colonial times': life under French rule on the isles of Mayotte
How France's approach to its overseas territories is stuck in the past
The long path to 'real equality' for France's overseas territories