PARIS (AFP) - French authorities arrested a suspected radical on Friday (May 5) close to an airbase, finding guns nearby as well as an allegiance pledge to the Islamic State in Iraq and Syria (ISIS) militant group and several of the group's flags in his car, sources close to the case said.

The pledge was on a computer flash drive discovered, along with the flags, in the former soldier's vehicle.

A shotgun and two vintage pistols were also discovered hidden near the base in Evreux, which is north-west of Paris, the sources said.

The discovery comes two days before France votes in the presidential election run-off.

Police arrested the suspect early Friday after finding his car near the base. Paris anti-terror prosecutors are investigating, but it is not clear why he was in the area.

The suspect, who was born in 1983, converted to Islam and has been under close surveillance since 2014 due to his radicalisation.

The election campaign has been overshadowed by security worries.

Karim Cheurfi, a 39-year-old Frenchman, shot and killed a police officer and wounded two others on the Champs Elysees avenue days before the first round of voting, in an attack claimed by ISIS. Cheurfi was killed by police gunfire.

Greenpeace activists on Friday pulled off a daring stunt in central Paris, attaching a giant banner to the Eiffel Tower and leaving police to admit security "flaws" at a time when terror fears remain high.