Syria's president exhorted his armed forces Wednesday to restore stability to the nation, which is reeling from a growing grassroots armed resistance and mounting deaths.

"The enemy is among us and is using inside agents to destabilize the country and the security of its citizens," President Bashar al-Assad said, according to the state-run Syrian Arab News Agency.

Al-Assad made his remarks as rebels fought with government soldiers for control of Aleppo, the country's most populous city and commercial hub.

Early Thursday, two activists reported that communications with the city were largely cut -- including cellular networks, landlines and Internet service. "There are whole neighborhoods where we do not know what's happening," an activist told CNN.

Seventeen people were killed Wednesday in the city, the opposition Local Coordination Committees of Syria said.

They were among 180 people killed nationwide Wednesday, including 104 in Damascus and its suburbs, 50 of whom were victims of a massacre in Jdeidet Artouz, and 27 in Yilda, the LCC said.

Col. Malek-Al Kurdi, deputy head of the Free Syrian Army in Aleppo, described the situation in Aleppo as promising for the rebel forces. "There is no way for Assad's ground troops or tanks to enter certain areas by land due to our strategic control of the highways," he said.

He said he is seeing an increase in the number of foreign jihadists. "The numbers are not big and they are not organized groups, they are more like individuals who are currently attached to some of our brigades on the ground," he said.

He cited Libyans, Yemenis and Tunisians who arrived with foreign funding, "mostly from Arabian Gulf private donors."

The LCC reported intense artillery shelling in Aleppo. Another opposition group, the Syrian Observatory for Human Rights, said on its Facebook page that fighting erupted in the Aleppo region "in the surroundings of a military base in the village of Handarat, which went on for hours." The group said a rebel leader was killed.

The U.N. Supervision Mission in Syria, which had been tasked with monitoring the U.N.-backed six-point peace plan, reported increased fighting and the use of heavy weaponry in the city over the past three days.

"Our observers are reporting exchange of fire, shelling and explosions in addition to use of helicopters, tanks, heavy machine guns and artillery shelling," said Sausan Ghosheh, a spokeswoman for the mission.

She said observers also said that opposition forces were equipped with heavy weaponry, including tanks.

"The U.N. has reminded both parties of their obligation under international humanitarian law to protect civilians," she said in the capital, Damascus. "We call on both sides to show utmost restraint and shift from this mindset of confrontation to a mindset of dialogue."

In Washington, acting Deputy State Department spokesman Patrick Ventrell blasted al-Assad for encouraging his troops.

"We think it's cowardly, quite frankly, to have a man hiding out of sight be exhorting his armed forces to continue to slaughter of the civilians of his own country," he said. "We think it's really despicable to be exhorting his armed forces to continue this slaughter and this bloodshed."

In Washington, two U.S. officials told CNN on Wednesday that President Obama has signed a secret "finding" authorizing covert, nonlethal support for rebels.

It was unclear exactly what the finding authorized and when it was signed, but the sources said it was within the past several months.

The Obama administration has ruled out arming the rebels for now, providing only nonlethal assistance, such as communications equipment.

The global debate on what to do about Syria may get renewed attention this month, as France assumed the rotating presidency of the U.N. Security Council.

France will call for a meeting this week to "try and stop the massacres and prepare for the political transition" in Syria, French Foreign Minister Laurent Fabius told French RTL radio Monday.

On Thursday, Under-Secretary-General for Peacekeeping Operations Hervé Ladsous is expected to report to the Security Council on the supervision mission, whose mandate was renewed late last month for 30 days.

Several signs indicate Syria's civil war is far from over, the International Crisis Group said Wednesday.

The combination of a regime fighting for survival, an Alawite sect whose members believe their fate hinges on the regime's and an opposition that is threatened by radicalization could indicate a prolonged civil war, the conflict resolution group said in a report.

"The regime will not succeed in suppressing the armed groups; if anything, its ruthless practices have guaranteed a virtually limitless pool of recruits prepared to fight with the opposition at any cost," the report said.