The crisis also deepened in the region when Turkey's deputy prime minister said Syrian forces opened fire on a second Turkish plane that was searching for the wreckage of a jet shot down last week by Damascus.
Turkey said it would push NATO to consider Syria's downing of the Turkish jet as an attack on the whole military alliance, and NATO's governing body is to meet Tuesday to discuss the incident. It's unlikely, however, that the alliance will take armed action against Syria.
Since the Syrian uprising began last year, thousands of soldiers, most of them low-level conscripts, have deserted and joined the rebels. High-level defections appear to be increasing.
According to a Turkish Foreign Ministry official, a brigadier-general defected to Turkey in recent days. If confirmed, it would be one of the highest-level defections. Gen. Mostafa Ahmad al-Sheik, who fled to Turkey in January, was the highest-ranking officer to bolt at the time.
The Turkish official spoke on condition of anonymity in line with government rules.
Turkey's state-run Anadolu news agency also said Monday that 33 soldiers defected overnight, including a general and two colonels.
Although the defections are notable, Assad's regime has remained remarkably airtight, particularly compared with the hemorrhaging of Moammar Gadhafi's inner circle in Libya in 2011.
Within weeks of the Libyan revolt, a number of Libyan ambassadors and other high-ranking officials quit the government, and many joined the opposition leadership. The early defection of huge sections of the army in eastern Libya gave the rebel movement a safe zone where they could freely organize their political and military strategies.
Syria has seen nothing similar, with armed groups fighting under the banner of the Free Syrian Army but lacking much coordination.
As Assad's crackdown on the uprising mutates into a civil war, fears are mounting that the violence could ignite regional unrest. Those fears were borne out Friday when Syrian forces shot a Turkish military plane out of the sky, saying the aircraft violated its airspace.
But Turkey disagrees. According to Turkish officials, the plane had unintentionally strayed into Syrian airspace, but it was inside international airspace when it was brought down. The jet's two missing crew members have not been found.
Both sides appear to be trying to calm tensions over the incident, which was a grim reminder of how quickly the Syrian conflict can bleed outside its borders.
Syria's Foreign Ministry spokesman said Monday that the plane was brought down by anti-aircraft fire. But he said his country has "no hostility" toward Turkey.
"We behaved in a defensive and sovereign way," Jihad Makdissi told reporters Monday in the Syrian capital, Damascus. He said the search was still under way for two missing Turkish airmen who were on the plane.
Bulent Arinc, Turkey's deputy prime minister, told a televised news conference Monday that Syrian forces fired on a CASA search-and-rescue plane following Friday's downing of an unarmed RF-4E reconnaissance jet. Arinc did not say whether the search and rescue plane was hit.
He said the Syrian side ceased firing after a warning from the Turkish military.
Arinc said Turkey retained its right to "retaliate" against what he called a "hostile act," but he added, "We have no intention of going at war with anyone."
Turkey will push NATO to consider the armed attack under Article 5 in a key alliance treaty, Arinc said. Article 5 states that an attack against one NATO member shall be considered an attack against all members.
The North Atlantic Council—which includes ambassadors of the 28 NATO countries—works by consensus and all members must approve any action. Tuesday's meeting comes after Turkey's requested ot under Article 4 of the treaty, which allows a NATO ally to seek such a consultation if it feels its territorial integrity or security has been threatened.
Asked if Turkey will insist on the activation of Article 5 of NATO, Arinc said, "No doubt, Turkey has made necessary applications regarding Article 4 and Article 5."
The prospect of Western military intervention in Syria remains remote, despite the tough talk. Such action is unlikely to get the support of either the U.N. Security Council or the Arab League, and outside intervention without the blessing of both of those bodies is all but unthinkable. There also is little appetite among NATO countries—of which the U.S. is the largest—for another war in the Middle East.
Unlike the military intervention that helped bring down Gadhafi in Libya, the Syrian conflict has so much potential for escalation. Syria has a web of allegiances to powerful forces including Lebanon's Hezbollah and Shiite powerhouse Iran.
Makdissi, the Syrian foreign ministry spokesman, said the meeting must not have an eye toward violating Syria's sovereignty.
"We heard statements from NATO and they have no intention of a military intervention in Syria. If the meeting is to be of hostile nature, I reassure everyone that Syrian land, waters and airspace are sacred for the Syrian army," he said.
EU foreign ministers condemned Syria's downing of a Turkish jet, but said the bloc will not support military action in the troubled country.
"What happened is to be considered very seriously (but) we do not go for any interventions," Dutch Foreign Minister Uri Rosenthal.
Still, the death toll in Syria is mounting as diplomatic attempts to solve the crisis fail. Activists say more than 14,000 people have been killed since the uprising began in March 2011.
Turkish Prime Minister Recep Tayyip Erdogan is expected to address parliament Tuesday and reveal what measures Turkey will take against Damascus for downing the plane.
Also Monday, the Red Cross said hundreds of civilians are trapped in the Syrian city of Homs and aid workers cannot reach them because of the fighting. Homs has been one of the hardest-hit areas in Syria as regime forces try to crush the opposition.
The defectors who crossed into Turkey overnight were taken to a refugee camp in Hatay, a province bordering Syria. Turkey is host to some 33,000 Syrians seeking refuge from the violence.
Anadolu said a total of 224 people crossed into Turkey overnight, a figure that includes the soldiers' families.
Last week, a Syrian fighter pilot flew his MiG-21 warplane to neighboring Jordan, where he was given asylum. The defection was a significant blow in part because the air force is particularly close to the regime. Assad's late father and predecessor, Hafez, was an air force pilot and commander before seizing power in 1970.
Fraser reported from Ankara, Turkey. Selcan Hacaoglu in Ankara contributed to this story.