France launched airstrikes Friday to help the government of Mali defeat al-Qaeda-linked militants who captured more ground this week, dramatically raising the stakes in the battle for this vast desert nation.

French President Francois Hollande said the "terrorist groups, drug traffickers and extremists" in northern Mali "show a brutality that threatens us all." He vowed that the operation would last "as long as necessary."

France said it was taking the action in Mali at the request of President Dioncounda Traore, who declared a state of emergency because of the militants' advance.

The arrival of the French troops in their former colony came a day after the Islamists moved the closest yet toward territory still under government control and fought the Malian military for the first time in months, seizing the strategic city of Konna.

For the past nine months, the Islamic militants have controlled a large swath of northern Mali, a lawless desert region where kidnapping has flourished.

"French armed forces supported Malian units this afternoon to fight against terrorist elements," Hollande said in Paris.

State of emergency in effect for 10 days 

He did not give any details of the operation, other than to say that it was aimed in part at protecting the 6,000 French citizens in Mali, where seven of them already are being held captive.

Residents in central Mali said they had seen Western military personnel arriving in the area, with planes landing at a nearby airport throughout the night.

Col. Abdrahmane Baby, a military operations adviser for the foreign affairs ministry, confirmed in the Malian capital of Bamako that French forces had arrived in the country but gave no details.

"They are here to assist the Malian army," he told reporters.

Traore went on national television Friday night to declare the state of emergency, saying it would remain in effect for 10 days and could be renewed.

He called on mining companies and nongovernment organizations to turn their trucks over to Malian military, raising questions about the army's ability.

State Department spokeswoman Victoria Nuland said the U.S. was "deeply concerned" by events in Mali, and that Washington was closely consulting with Paris. She said neither France nor Mali has asked for U.S. military assistance.

France has led a diplomatic push for international action in northern Mali but efforts to get an African-led force together, or to train the weak Malian army, have dragged.

The French quickly mobilized after the Islamists seized the city of Konna on Thursday, pushing closer to the army's major base in central Mali.

The United Nations Security Council has condemned the capture of Konna and urged UN member states to assist Mali "in order to reduce the threat posed by terrorist organizations and associated groups."