A French court has upheld a ban on a Muslim engineer from accessing nuclear sites, citing his links with what it termed as "jihadist networks", but his lawyer called it a case of Islamophobia.

Lawyer Sefen Guez Guez told AFP news agency on Monday that he was looking at launching an appeal.

The 29-year-old working for a firm subcontracted by energy giant EDF had been granted access to nuclear installations as part of his job throughout 2012 and 2013.

But in March this year, the man - who cannot be named according to French law, had his pass to enter the Nogent-sur-Seine nuclear power station revoked.

Officials said he had links with a violent armed group and that he was in touch with an imam involved in recruiting people to fight in Iraq.

A court in the north-eastern town of Chalons-en-Champagne upheld the ban saying the management could prevent those "undergoing a process of political and religious radicalisation" from accessing sensitive sites.

The lawyer for the man cried foul and argued that his client had no police record.

"There is no proof of these supposed links," Guez Guez said.

In June 2014, Guez Guez successfully had the ban revoked by an appeals court. But when the engineer turned up for work, he found he was once again refused access - this time by EDF - to his place of work, and his lawyer appealed again.

France is home to some five million Muslims - the largest Muslim population in western Europe.

Like a number of European countries, France has expressed concern over young people leaving the country to fight in Iraq and Syria, and who could pose a risk to domestic security on their return.

According to official estimates, about 800 French nationals or residents, including several dozen women, have travelled to Syria, returned from the conflict-ridden country or plan to go there.