There are fears of an upsurge in separatist violence on the island

Justice Minister Dominique Perben is to visit the island next week to meet judges, law enforcement officials and prison guards to reassure them that efforts are being made to ensure their safety.

Workers at a low-security prison on Corsica's eastern coast called for talks with the minister after a triple bomb attack on the facility on Monday that allowed four inmates to escape. No-one was injured in the blasts.

The decades-old campaign of low-level violence by Corsican separatists has picked up in recent weeks, ever since the conviction in July of eight separatists involved in the 1998 assassination of the island's governor, Claude Erignac.

It also seems to have coincided with a referendum on greater autonomy which was narrowly defeated last month.

"We have to tell people there that the state will ensure that law is enforced and that the people who live in this part of France have recourse to justice," Mr Perben told French radio.

Earlier on Thursday, police discovered three unexploded bombs hidden near posts used by police and customs agents at the airport near Corsica's biggest city, Ajaccio.

Police were alerted to the explosives by an anonymous call to a local television station from members of a splinter group of the main separatist organisation, the Corsican National Liberation Front (FLNC).

Long-running campaign

Militant separatists have been campaigning for three decades to break away from France.

One of their main tactics has been the bombing of holiday homes owned by non-Corsicans, as well as targeting police stations, prisons and other symbols of French rule.

The defeat of a referendum last month over limited autonomy in return for an end to the attacks also angered the separatists, who saw the proposal as a first step towards self-rule.

In July, a dozen people were slightly wounded when two blasts damaged regional tax and customs offices in the French Riviera city of Nice.