Turkey has toughened its response to Syria's downing of a Turkish military jet last week, saying it will ask fellow NATO members to consider the incident a Syrian attack on the whole alliance.

NATO envoys are due to meet Tuesday at Turkey's request, to discuss a reaction to the attack on the Turkish reconnaissance aircraft near the Syrian-Turkish maritime border. Turkish Deputy Prime Minister Bulent Arinc Monday said Ankara called the meeting under Article 5 of the NATO treaty, which states that an attack on one alliance member shall be considered an attack against all members.

NATO previously said Turkey requested the meeting by invoking Article 4 of the treaty that allows one member to hold consultations with others if it feels its security has been threatened.

Speaking after a Turkish Cabinet meeting, Arinc said Ankara has the right to retaliate under international law for what he called Syria's “hostile” act against the unarmed military jet. He accused Syrian forces of deliberately shooting down the aircraft in international airspace over the Mediterranean. But Arinc also said Turkey does not want to go to war over the incident, which left two Turkish pilots missing.

Syria disputes the Turkish accusation.

Syrian Foreign Ministry spokesman Jihad Makdissi said Monday a Syrian anti-aircraft machine gun fired on the Turkish jet in self-defense as it was flying low along the Syrian coast in violation of his country's sovereignty. He said the machine gun has a maximum range of 2.5 kilometers.

Turkey has said its plane inadvertently entered Syrian airspace for a brief period before leaving and then being struck by Syrian fire.

Makdissi said Syria remains committed to neighborly relations with Turkey. But he also warned Ankara and other NATO members against considering hostile action against Syria, saying they should be mindful that Syrian land, territorial waters and airspace are “sacred.”

In his remarks to reporters, Turkish Deputy Prime Minister Arinc said Syrian forces fired at a second Turkish military plane that was searching for the downed reconnaissance jet. He did not say if the search aircraft was hit. Arinc said Turkish Prime Minister Recep Tayyip Erdogan will give more details of Turkey's response to the Syrian actions on Tuesday in remarks to lawmakers in parliament.

U.S. State Department spokeswoman Victoria Nuland said Washington looks forward to Tuesday's NATO meeting “to hear (Ankara's) views of this incident and to hear what they want to do moving forward.” She also described Syria's attack on the reconnaissance jet as unprovoked.

“There was no warning to this aircraft. It was just shot out of the sky. And that obviously is not in keeping with international norms in such incidents.”

EU foreign policy chief Catherine Ashton said Monday she expressed concern about Syria's downing of the jet in a conversation with the Turkish foreign minister.

“We are very concerned about what has happened and very concerned for the family of the two pilots who are missing. And we will be obviously looking to Turkey to be restrained in its response.”

British Foreign Secretary William Hague downplayed the prospect of the aircraft incident triggering foreign military intervention in Syria.

“I do not think it illustrates a different phase of the Syrian crisis. I think we continue to be in a great danger of a collapse in Syria or of intensifying conflict.”))

In other developments, EU foreign ministers meeting in Luxembourg approved new sanctions on Syrian President Bashar al-Assad's government, adding one Syrian official and six companies and entities to an EU sanctions list. The sanctions are aimed at pressuring Mr. Assad to stop his deadly crackdown on a 15-month uprising against his 11-year rule.

Turkish media and officials Monday said a Syrian general and other senior military officers defected to the opposition by crossing into Turkey overnight with their families. The mass defection raised the number of Syrian generals who have sought refuge in Turkey to 13.

Turkey has provided sanctuary to Syrian military defectors and thousands of Syrian refugees since last year, when it turned against President Assad in protest at his suppression of the revolt.

Activists posted a video on the Internet showing what they said was Syrian government shelling of rebellious communities in the central province of Homs Monday.

Separately, U.N. and diplomatic sources told Reuters news agency that a top U.N. human rights official was in Syria Monday for talks with the government on opening an investigation into massacres and other atrocities in the country. If confirmed, it would be the first time Brazilian expert Paulo Pinheiro has been granted permission to enter Syria since the U.N. Human Rights Council set up his team in September.

(Scott Stearns in Washington contributed to this report)