Paris: French President Francois Hollande today rejected opposition calls to further harden anti-terrorism legislation after the country's second jihadist attack in two weeks.

"Restricting our freedoms will not make the fight against terrorism more effective," he said, adding that changes made to legislation already gave authorities sufficient "capacity to act".

He was speaking after two jihadists attacked a church in a Normandy town, killing an elderly Catholic priest by slitting his throat, and severely injuring another person.

Hollande's predecessor and opposition chief Nicolas Sarkozy earlier called for the government to "thoroughly change ... The strategy of our counterattack."

"Our enemy has no taboos, no limits, no morals, no borders," he said, asking the government to adopt proposals made by his right-wing Republicans party.

The opposition wants anyone suspect of being radicalised to be placed in detention and to prevent convicted terrorists from being released from prison after having served time, if they are still considered dangerous.

The Republicans also wants to make it a criminal offence to have spent time in the "field of terrorist operations", namely Syria and Iraq.

However those returning from jihad are already charges with criminal conspiracy with a terrorist enterprise.

"The government is using all human and material means to fight this threat, with a mobilisation of police, gendarmes and soldiers never before seen in the Fifth Republic," said Hollande.

The president has urged unity in a country poisoned by bitter political blame-trading over security failings after a Tunisian national mowed down a crowd celebrating Bastille Day on July 14, killing 84.

"What the terrorists want is to divide us, separate us, to tear us apart. We must avoid one-upmanship, arguments, conflation, suspicions," he said.

"This war will be long. Our democracy is the target, and it will be our shield. Let us stand together. We will win this war."