PARIS (AFP) - France has ordered tightened security, including anti-terrorist measures, following action against radical Islamists both in Mali and Somalia, President Francois Hollande said Saturday.

Mr Hollande said France "has to take all necessary precautions" in the face of a terrorist threat, including "surveillance of our public buildings and our transport network." The French leader evoked Vigipirate, France's national security alert system, created in 1978 and updated several times.

The move came after a botched French commando raid in Somalia to free an intelligence agent which killed at least 18 people including a French soldier,and also the deployment of French air power to help the army in Mali stop Islamist rebels from advancing south.

The Vigipirate system defines four levels of threats represented by five colors: white, yellow, orange, red and scarlet.

The levels call for specific security measures, including increased police or police-military mixed patrols in subways, train stations and other vulnerable locations.

The highest level scarlet includes measures that are highly disruptive to public life. France has maintained a second level, red, since the London bombings in July 2005.

The top level was briefly in force in France's south-western Midi-Pyrenees region after Islamist gunman Mohamed Merah went on a shooting spree in March last year killing seven people.