State military forces on Friday retook a key town in northern Mali after intense fighting that included help from French military forces, a defense ministry spokesman said.

"Today, we have recaptured Konna," said the spokesman, Diaran Kone, at a briefing played over state radio.

The Mali city of Konna had been seized by Islamist forces on Thursday as they pushed southward from their strongholds in the desert of northern Mali.

"The fighting lasted for not more than two, maybe three hours; Konna was recaptured with the assistance of French, Nigerian and Senegalese troops this afternoon," said Kone. "All measures were used, including the drones given by France."

Earlier, Nigeria's defense minister had denied to CNN that Nigerian troops were involved in Friday's fighting.

But France confirmed that its armed forces had taken part in the fighting and launched airstrikes in support of the operation.

French President Francois Hollande announced that French ground and air forces were in the country to aid government forces.

"French military forces have brought their support to the Malian forces this afternoon to fight against these terrorist elements," said Hollande, speaking from the Elysee Palace in Paris. "This operation will last as long as it is necessary. I will regularly inform the French people about its course."

It was not clear how many French troops were deployed. But French Foreign Minister Laurent Fabius said the French military has also launched airstrikes.

Mali's interim president, Dioncounda Traore, declared a state of emergency across the country Friday and called for "a general mobilization" to defend against the advance of radical Islamists.

He acknowledged France's military help, including air support.

Hollande said Mali "is facing a terrorist aggression in the north," and added that "the whole world is aware" of the terrorists' "brutality and extremism."

"Today, it is therefore the very existence of this friendly state that is at stake, as is the security of its population and of our own 6,000 citizens living there," he said.

France, which has posted troops in many locations in Africa, had said it wouldn't send combat troops to Mali and had pledged to scale back on intervening in local politics and conflicts in Africa. For example, it declined a request to intervene in the Central Africa Republic, where an insurgency flared.

So the Mali operation underlines the seriousness of France's concern over its former colony. French hostages have been taken in neighboring Niger by al Qaeda in the Islamic Maghreb; Paris is trying to contain any further militant expansion in the heart of Africa.

Northern Mali has been occupied by radical Islamists, who moved in after fighting broke out in January 2012 between government forces and Tuareg rebels. West African states and international leaders, worried about an al Qaeda foothold, say a rapid military intervention is essential to solving the security crisis in Mali.

Hundreds of thousands of Malians have been uprooted because of proliferation of armed groups, drought and political instability after a coup d'etat in March.

Hollande said the country is consulting with the United Nations and "intervening within the framework of international law." Parliament will be consulted as soon as Monday on the operation, he said.

"The terrorists must know that France will always be there whenever the rights of a country that strives for freedom and democracy are threatened, not just when its core interests are at stake," he said.

Europe, Fabius said, "has made some decisions to train and reshape the Malian army."