Turkish Foreign Minister Ahmet Davutoglu phoned world powers to brief them about the downing of one of Ankara's planes by Syria as a joint search for the airmen, who were shot down over the Mediterranean, tried to locate them.

Signals from both sides suggested neither wanted a military confrontation over Friday's incident as the search focused its efforts near a Turkish province that hosts thousands of rebels fighting President Bashar al-Assad.

Given the hostility between the two former allies over Assad's 16-month-old crackdown on his opponents, the joint operation was likely to sit uneasily with both countries.

Iraq, which borders both, said the incident marked a serious escalation of the Syrian conflict, demonstrating its potential to affect other countries in the region.

'No country is immune from this spillover because of the composition of the societies, the extensions, the connections, the sectarian, ethnic dimensions,' Iraqi Foreign Minister Hoshiyar Zebari said in Baghdad. 'This is not an excuse to do nothing about Syria, no. But there will be an impact.'

Turkey has declared it will respond decisively.

'It is not possible to cover over a thing like this. Whatever is necessary will no doubt be done,' Turkish President Abdullah Gul told reporters, adding that Ankara had been in telephone contact with the Syrian authorities.

Davutoglu, Turkey's foreign minister, on Saturday evening phoned foreign ministers from the United States, Britain, France, Russia, and Iran as well as the European Union's foreign policy chief Catherine Ashton, a spokesman for the foreign ministry said. He had briefed them about Turkey's evaluation of the incident, the spokesman added.

The plane's downing showcased Syria's Russian-supplied air defences - one of the many reasons Western powers are loathe to intervene to halt bloodshed in the country.

UN Secretary-General Ban Ki-moon urged Turkey and Syria to handle the matter with restraint, using diplomatic channels.

Turkey's Deputy Prime Minister Bulent Arinc said the downed jet was a reconnaissance aircraft. Turkish media had said it was an F-4 Phantom, a fighter also used for reconnaissance.

According to a Syrian military account, the Turkish plane was flying fast and low, just one kilometre off the Syrian coast when it was shot down. It had been tracked at first as an unidentified aircraft and its Turkish origin established later.

'The navies of the two countries have established contact. Syrian naval vessels are participating along with the Turkish side in the search operation for the missing pilots,' it said.

With the second biggest army in Nato, a force hardened by nearly 30 years of fighting Kurdish rebels, Turkey would be a formidable foe for a Syrian military already struggling to put down a popular uprising and an increasingly potent insurgency.

A civil war is already in full swing in Syria, where fighting or shelling engulfed parts of the cities of Aleppo, Hama, Homs, Deir al-Zor and Douma, according to the British-based Syrian Observatory for Human Rights.

Davutoglu met Turkey's military commanders and intelligence chief to discuss the search for the pilots and Ankara's next steps. He was due to make a statement about the incident on state TV on Sunday morning.

Prime Minister Tayyip Erdogan held two security meetings with senior officials, less than 24 hours after he convened a crisis session on Friday evening.

Separately, he called a meeting with the leaders of the country's main opposition parties for Sunday. 'Turkey will present its final stance after the incident has been fully brought to light and decisively take the necessary steps,' Erdogan's office said.

Turkish newspapers were less restrained.

'They (the Syrians) will pay the price,' said Vatan, while Hurriyet daily said: 'He (Assad) is playing with fire.' - Reuters