"The terrorists' breakthrough must be stopped," he said. "If not, it's the entire Mali that falls into their hands, with a threat to the whole of Africa and Europe."
The U.N. Security Council cited "grave concern over the reported military movements and attacks by terrorist and extremist groups" in northern Mali.
"This serious deterioration of the situation threatens even more the stability and integrity of Mali and constitutes a direct threat to international peace and security," the council said.
Last month, the council authorized a one-year military peacekeeping mission in Mali. The African-led International Support Mission in Mali aims to help rebuild Mali's security and defense forces and to help Malian authorities recover the areas in the north.
A regional group, the Economic Community of West African States, has pledged thousands of troops to the mission, and the Security Council has urged other member states to contribute troops.
The Malian government and rebel groups are expected to meet January 21 for peace talks in Burkina Faso's capital, Ouagadougou.
Mali held its first democratic elections in 1992, after decades of military rule.
It maintained a strong democracy until March, when a group of soldiers toppled the government, saying it had not provided adequate equipment for them to fight ethnic Tuareg rebels roaming the vast desert in the north.
Tuareg rebels, who for decades had staged rebellions seeking independence, took advantage of the power vacuum and seized parts of the north. The rebels had fought alongside Libyan leader Moammar Gadhafi and returned to Mali -- with their weapons in tow -- after he was killed in October 2011.
A power struggle then erupted in the north between the Tuaregs and local al Qaeda-linked radicals, who seized control of large parts of the desert north. The international community voiced concerns about al Qaeda in the Islamic Maghreb and its expanding presence in Mali.
The al Qaeda wing is linked to the attack last year in Benghazi, Libya, that killed the U.S. ambassador to Libya and three other Americans, U.S. officials have said.
The militants in the north have applied their strict interpretation of Sharia law by banning music, smoking, drinking and watching sports on television. They also publicly stoned a couple to death in July, reportedly for having an affair.
Public executions, amputations, floggings and other inhumane punishments are becoming common, the United Nations says.
The militants have attacked Timbuktu's historic tombs and shrines, claiming the relics are idolatrous. The picturesque city was once an important destination for Islamic scholars because of its ancient and prominent burial sites, and it is a UNESCO World Heritage Site.
Tuareg rebels retreated from the well-armed militants but have vowed to fight back and establish in the north their own country, which they call Azawad.