French President Jacques Chirac has expressed his regret that Corsican voters have rejected autonomy plans, warning that separatist violence will not be tolerated.
Four holiday homes were blown up after the vote
The Mediterranean island's 260,000 inhabitants voted by a tiny margin to reject the plans in a referendum on Sunday.
The Corsicans were being offered a new national assembly with tax-raising and greater control over public services, in a bid to end 30 years of separatist violence.
Amid fears of a fresh upsurge in unrest, four bombs exploded overnight on Sunday, destroying holiday homes belonging to French people from the mainland.
My priority in the months to come will be to ensure the security of the island and public order - the days of impunity are over
French Interior Minister
Even before the vote, separatist anger had been increased by the arrest of France's most wanted man, Yvan Colonna, just before the vote.
French Interior Minister Nicolas Sarkozy warned that his security forces would now get tough with separatists.
"My priority in the months to come will be to ensure the security of the island and public order," he said in a statement. "The state cannot be absent from Corsica. The days of impunity are over."
Mr Sarkozy had made eight visits to the island in the past 14 months to push for a Yes vote, and its rejection was seen as a personal blow to him.
Mr Chirac joined his interior minister in insisting that further unrest would be combated.
"The Corsicans did not agree to the proposal to reorganise the institutions of their region. This, I regret," he said in a statement.
"The future of the island depends on the nation's solidarity and the
state's determination to confront all forms of violence."
Colonna's arrest angered some nationalists
French newspapers on Monday pointed to several factors which may have contributed to the No vote.
The arrest of Mr Colonna, which sparked fury among some separatist supporters, may have persuaded them to reject the plans as a sign of their anger.
The French battle over pension reforms may also have played a part. Mr Sarkozy said public sector officials had refused to support the plan in order to protest against the plans to make them work longer to claim a full pension.
We are now going to continue our fight for sovereignty and, eventually, independence
Corsica Nazione party
Another theory suggested that the public sector workers feared that their future careers could be limited by separation.
Other Corsicans feared that if they voted Yes, the assembly could be dominated by the separatists, even thought opinion polls show most on the island wish to remain French.
Independence campaigners said their battle for autonomy was not over.
"We are now going to continue our fight for sovereignty and, eventually, independence," said one separatist
assembly member, Paul Quastana of the Corsica Nazione party.
The BBC's Caroline Wyatt in Paris says that, regardless of the result, many on Corsica hope the referendum has focused minds in Paris on the island's real needs.
Corsican 'Robin Hood'
She says some on the island believe it is no coincidence France was able to announce the capture of Mr Colonna just before the vote.
He was wanted in connection with the murder of the most senior French official on Corsica, Claude Erignac, in 1998.
The murder was the highest profile assassination by Corsican separatists. Eight other Corsicans are already on trial in Paris for aiding and abetting the murder.
The trial may now be suspended, days ahead of its anticipated end, so that it can restart with Mr Colonna joining the defendants in the dock.