Recep Tayyip Erdogan, Turkey's prime minister, has spoken about his country's tense relations with Damascus ahead of a special meeting of NATO allies to discuss the shooting down by Syria of a Turkish warplane last week.
Ambassadors to the military alliance will meet in Brussels on Tuesday at Ankara's request, in an incident which Turkey has branded an "act of aggression".
Condeming the government of Bashar al-Assad in his weekly address to parliament, Erdogan said: "The United Nations and Kofi Annan gave him [Assad] a plan, but he did not take it seriously.
"The Syrian regime has no more legitimacy, that is clear. Women, children, the elderly, have been killed relentlessly by this tyranny."
However, Erdogan also stated that: "Syria's borders can never prevent the brotherhood between Syria and Turkey."
It is only the second time in NATO's 63-year history that it will convene under Article 4 of its charter, which provides for consultations when a member state feels its territorial integrity, political independence or security is under threat.
The only other time NATO has convened under Article 4 was in 2003 to discuss the Iraq war, again at the request of Turkey.
Turkey rejected assertions from Damascus that its forces had no option but to fire on the F-4 jet as it flew over Syrian waters close to the coast on Friday.
In a letter to the UN Security Council, Turkey condemned the "hostile act by the Syrian authorities against Turkey's national security", saying it posed "a serious threat to peace and security in the region".
The Security Council will also hold consultations on Syria at 14:00 GMT on Tuesday.
Bulent Arinc, Turkey's deputy prime minister, said on Monday that Syrian troops had also opened fire on a rescue plane searching for the pilots who were shot down on Friday.
"One of our CASA planes took off with a rescue team. Unfortunately, shots from the ground targeted our plane," Arinc said during a news conference,
"Our foreign ministry and our military command notified Syrian authorities and this harrassment ceased immediately."
He added that Syria's actions "would not go unpunished".
The incident has further heightened tensions between Turkey and Syria already strained to near breaking point over the 16-month uprising against Syrian President Bashar al-Assad's rule.
European Union foreign ministers called on Monday for Turkey to show restraint, saying they would increase pressure on Assad.
"Military intervention in Syria is out of the question," Dutch Foreign Minister Uri Rosenthal said.
'Act of defence'
Syria's description of the event on Monday as an act of self-defence, though tempered with commitment to a "neighbourly relationship", seemed likely to further anger Ankara.
"The plane disappeared and then reappeared in Syrian airspace, flying at 100 metres altitude and about 1-2kms from the Syrian coast," Jihad Makdissi, Syrian foreign ministry spokesman, told a Damascus news conference.
"We had to react immediately, even if the plane was Syrian we would have shot it down.
"The Syrian response was an act of defence of our sovereignty carried out by anti-aircraft machinegun which has a maximum range of 2.5 km."
Syria warned Turkey and NATO against retaliating.
"NATO is supposed to be there to strengthen countries," said Makdissi. "If their meeting is for hostile reasons [they should know that] Syrian land and waters are sacred."
The unarmed reconnaissance jet had briefly entered Syrian airspace as it approached land after patrolling the eastern Mediterranean, Arinc said, but was warned by Turkish radar controllers and immediately left and turned again out to sea.
It then made another approach to land when it was shot down 13 miles off the coast in international airspace, he said, out of the reach of Syria's anti-aircraft guns.
"According to the data in our hands, it points to our plane being shot by a laser or heat-guided surface-to-air missile," he said.
"The fact our plane was not given an early radar warning, suggests it was not a radar-guided missile."
By invoking Article 4 of the NATO charter, rather than Article 5 which calls for military action, Turkey has signalled it wants action against Syria short of armed intervention.
The Anadolu agency said on Monday that the group, which included a general and two colonels, crossed into Turkey overnight and that they were being hosted at a refugee camp near the border.
The defection brought to 13 the number of generals seeking refuge in Turkey since the revolt against Syrian President Bashar al-Assad's regime erupted 16 months ago.
Thousands of soldiers have abandoned the army, but most are low-level conscripts. The Free Syrian Army, the loosely-linked group of rebel forces, is made up largely of defectors.
Meanwhile, in shell-shattered districts of Homs, the heart of the uprising against Assad and the city where the latest defectors were reported to have come from, rebels battled troops as aid workerstried to evacuate civilians.
In-depth coverage of escalating violence across Syria
The International Committee of the Red Cross (ICRC) said it was again trying to arrange a safe evacuation of trapped civilians from Homs.
But anti-government activists reported heavy shelling on central districts, including Jouret al-Shiyah and al-Qarabis.
Video showed detonations and machine gun bursts from the skeletal remains of abandoned apartment blocks.
Amateur video obtained by the Reuters news agency reportedly showed rebel fighters in control of a Syrian military base in the northern town of Daret Ezzah in Aleppo province. Al Jazeera was not able independently verify the pictures.
A spokesman for the fighters said they were only able to capture the air defence base after heavy fighting and with the help of defectors.
The activist Syrian Observatory for Human Rights said Assad's troops had carried out raids and arrests in areas still under army control.
Heavy fighting between government forces and rebel fighters was also reported in the opposition centres of Idlib, Deir Al Zor and Deraa, the birthplace of the uprising.
The UN has said more than 10,000 people have been killed by government forces, while Syria has said at least 2,600 members of the military and security forces have been killed by what it calls foreign-backed "terrorists".