Fears of an Islamist revenge attack have prompted French president Francois Hollande to order an increase in domestic security.
French forces intervened against Islamist rebels in the west African nation of Mali on Friday, where reports say scores of people have already been killed in French air strikes.
Within hours of the intervention in Mali, French soldiers failed in an attempt to release a hostage in Somalia, but government officials said the operations were not connected. One soldier was killed, another is missing and the fate of the hostage, a French intelligence agent, is not clear.
Security was to be stepped up at public buildings and transport networks, particularly rail and air, the BBC reports. Public gatherings will also be affected.
France made the decision to deploy troops in Mali after the army lost control of a strategically important town to Islamists who were advancing south. The rebels took control of a huge swathe of northern Mali last April.
The central town of Konna has since been recaptured, the Malian government says.
Reuters reports more than 100 people including rebels and government soldiers were killed during French air strikes and fighting over Konna, citing Malian military sources and witnesses.
UK support
Britain says it will give logistical support to France to help transport troops and equipment to Mali but will not send in any combat forces.
A Downing Street spokesperson has said Prime Minister David Cameron and Mr Hollande discussed the crisis in Mali in a phone call, the BBC reports.
Mr Cameron agreed to provide two transport planes which will be deployed quickly and used to fly in more foreign troops and equipment.
A group of West African countries has authorised the immediate deployment of 2000 soldiers to Mali.
