Condé-sur-Sarthe (France) (AFP) - Prison guards blocked access to 18 jails on Wednesday to protest working conditions after the stabbing of two guards by a radicalised inmate.

Dozens of officers from a high-security facility at Conde-sur-Sarthe in northern France, where the knife attack took place on Tuesday, set fire to tyres and pallets.

Guards at another 17 of France's 188 prisons joined in on Wednesday morning to highlight complaints about the dangers of Islamist extremists and the spread of hardline ideologies behind bars.

"Feelings are running high because we've been saying for a long time that this would happen," Emmanuel Guimaraes, a representative from the FO union, told AFP outside the Conde-sur-Sarthe facility.

There are fears of a re-run of January 2018 when officers picketed jails for three weeks after an attack by an extremist that left three guards with injuries in northern France.

The perpetrator of Tuesday's bloodshed was a mentally unstable 27-year-old former homeless man already serving a 30-year prison sentence for violent crime.

Named as Michael Chiolo, he was lightly injured on Tuesday evening when armed police raided a room where he holed up with his pregnant girlfriend after stabbing the guards with a ceramic knife.

His partner -- suspected of smuggling in the knife -- was killed in the assault.

The couple had intended to marry, according to Chiolo's former lawyer.

Prosecutor Remy Heitz said Chiolo wanted to "avenge" the death of Cherif Chekatt, a criminal and extremist who shot dead five people in Strasbourg in December before being killed by security forces.

The two men had shared a cell at a prison in Epinal, eastern France, a security source told AFP.

Chiolo, a Muslim convert of Italian origin, is serving a 30-year sentence for kidnapping an 89-year-old concentration camp survivor in 2012.

His gang got away with 300 euros ($339) and a handful of war medals, leaving the tied-up victim to choke to death.

Story continues

Chiolo was heard shouting "Allahu Akhbar" (God is Greatest) during his rampage in a family-visiting area, staff representative Alassanne Sall told AFP on Tuesday.

- 'Flaws' in security -

Justice Minister Nicole Belloubet Wednesday acknowledged "flaws" in security procedures, adding that there would be a full investigation into how Chiolo was able to obtain the knife used in his attack.

"There's no reason why visitors shouldn't be body-searched, and if they refuse, not be allowed into the prison," she told RMC radio.

Of the 70,000 people in jail in France, some 500 have been condemned on terrorist-related charges, and 1,200 ordinary inmates have been classified as "radicalised", the minister.

All of the "radicals" would eventually be housed in special secure prison wings.

The investigation into Tuesday's stabbing is likely to assess why Chiolo was not housed in his prison's special wing despite being radicalised.

The first "jihadist attack" launched from within a prison in France took place in September 2016, according to prison authorities.

A Moroccan, jailed for attempting to travel to Syria to join jihadists, attacked two guards with a knife at a prison in Osny, northwest of Paris, saying he was acting on behalf of the Islamic State group.

Then in January 2018, a German Islamist extremist, Christian Ganczarski, jailed for helping organise an attack against a synagogue in Tunisia, stabbed three prison guards at Vendin-le-Vieil, a high-security jail in northern France.

Experts and trade unions have raised the alarm about the spread of extremism in French prisons, leading the government to step up construction of new facilities to house dangerous individuals.

France has suffered a series of deadly attacks since 2015 and is on high alert amid concerns about the return of Islamic State group jihadists from Syria.