Syrian President Bashar al-Assad says the city of Aleppo, the economic center of Aleppo province, will "return stronger than ever," after Syrian forces retook complete control from rebel fighters.

In a rare televised address Monday, Assad said the military will not give up until it achieves total victory "sooner or later."

"This liberation does not mean the end of the war, and does not mean the end of the schemes, not the end of terrorism or the surrender of enemies. ... It means that we rubbed their noses in the dirt as a prelude for complete victory."

Assad said the fight to liberate all of Aleppo along with neighboring rebel-controlled Idlib province will continue, despite the "empty noise" from the North - a reference to Turkey, which borders both provinces and has backed the rebels.

Turkey has sent troops and equipment into Idlib to try to hold off the Syrian military advance, while Turkish diplomats are in Moscow for talks with Russia, Assad's biggest ally.

A statement from the Turkish Foreign Ministry Monday "stressed the need to quickly reduce tensions on the field and to prevent further deterioration of the humanitarian situation."

Syrian forces backed by Russian air power have taken control over most of Aleppo, seizing about 30 villages in just a single day Sunday. Aleppo city had been the target of constant rebel rocket fire.

U.N. humanitarian chief Mark Lowcock says the fighting in northwest Syria, including Idlib, has reached a "horrifying level," with about 900,000 civilians forced to flee their homes since early December.

"The biggest humanitarian horror story of the 21st century will only be avoided if Security Council members and those with influence overcome individual interests and put a collective stake in humanity first," Lowcock said.

U.S. officials have condemned the Syrian government's offensive on Idlib, expressing Washington's support for Turkey after its forces came under attack by Syrian troops.

"The United States once again condemns the continued, unjustifiable and ruthless assaults on the people of Idlib," U.S. Secretary of State Mike Pompeo said in a recent statement.

"We stand by our NATO ally Turkey in the aftermath of the attack, which resulted in the death of multiple Turkish personnel serving at an observation post used for coordination and de-escalation, and fully support Turkey's justified self-defense actions in response," Pompeo added.