French police have blocked the entrance to a cemetery to stop the inauguration of a memorial to paramilitaries who fought against Algerian independence.
The memorial pays tribute to right-wing militants killed during their failed campaign in the 1960s.
The memorial in the village of Marignane was put up surreptitiously on Tuesday by a group called Adimad.
Around 600 sympathisers turned up for the ceremony, which was banned by the local authorities.
Some laid a wreath outside the cemetery before dispersing.
Adimad stands for the Association for the Defence of the Moral and Material Interests of Former Prisoners and Political Exiles of French Algeria.
Algeria's eight-year fight for independence started in 1954, and brought to an end 132 years of French colonial rule. The fighting was brutal, with atrocities committed on both sides, and resulted in an estimated 500,000 deaths.
The rebel Secret Armed Organisation (OAS) was formed by disgruntled French soldiers in 1961 as it became clear that the French government was moving towards a settlement with Algerian insurgents.
Among those honoured by the memorial are four men executed for their part in the OAS guerrilla campaign in the early 1960s.
They include Jean-Marie Bastien-Thiry, who masterminded an attempt to kill the late French leader, General Charles de Gaulle, in Paris in 1962.
The bronze statue in Marignane is dedicated to "Fighters shot by firing-squad or otherwise killed so that French Algeria could live".
Human rights groups and relatives of Algerian veterans of the war held a counter-demonstration at the village, which is near Marseille in the south of the country.
Mouloud Aounite, President of the Movement against Racism and for Friendship between Peoples (MRAP) said the planned ceremony was an insult and showed "contempt for the nation which condemned these murderers".
"This inauguration is destroying our memories. In this current context of tension, this type of initiative is a way to set things ablaze," she told France Info Radio.