Turkey on Saturday played down the loss of a warplane to Syrian air defences as President Bashar al-Assad announced a new cabinet with key posts unchanged and dozens of people were killed nationwide.

NATO member Ankara acknowledged that one of its jets may have violated Syrian airspace after Damascus confirmed shooting down the F-4 Phantom on Friday, in comments seen as a bid to cool the latest spat between the former allies.

"An unidentified aerial target violated Syrian airspace, coming from the west at a very low altitude and at high speed over territorial waters," a Syrian military spokesman told the official SANA news agency.

Anti-aircraft batteries hit the plane about a kilometre from the coast and it crashed some 10 kilometres (six miles) off Latakia province, he added.

Turkish President Abdullah Gul said it was not unusual for warplanes flying at high speed to cross maritime borders, stressing that such actions were not "ill-intentioned."

Naval forces from both nations were searching for the two missing crew.

Key Turkish ministers were meeting to discuss future steps, a foreign ministry diplomat told AFP, after Prime Minister Recep Tayyip Erdogan said Ankara "will announce its final position and take necessary steps with determination after the incident is entirely clarified."

Meanwhile, Assad announced the formation of a new government with the key foreign, defence and interior ministry portfolios unchanged, as monitors said at least 48 people were killed in violence across the country.

The announcement came less than two months after controversial parliamentary elections boycotted by the opposition.

"President Bashar al-Assad has issued Decree 210 forming a new government under Prime Minister Dr Riad Hijab," state television said.

Foreign Minister Walid al-Muallem remains in his post, along with the defence and interior ministers, Daoud Rajha and Mohammad al-Shaar.

Rajha, in the post since August, was among those sanctioned by the United States for his role in the deadly crackdown on Syrian protesters.

Abdel Basset Sayda, head of the main opposition Syrian National Council, dismissed the new line-up as a sham aiming "to give the impression that reforms have been brought in."

He said there was "no real change," with key posts unchanged.

The new cabinet assumes power amid an intensification of repression and clashes, which last week led to the the halt of the United Nations observer mission.

The Britain-based Syrian Observatory for Human Rights said most of the dead on Saturday were civilians, killed by security forces as the army pressed its campaign against rebel strongholds.

On Friday, at least 116 people, among them 69 civilians, 31 members of pro-regime forces and six rebels, died nationwide.

The International Committee of the Red Cross condemned the killing of a Syrian Arab Red Crescent volunteer, in the fourth such incident in the country's deadly unrest.

Bashar al-Youssef, 23, was shot and fatally wounded on Friday in Deir Ezzor in eastern Syria, the two organisations said in a joint statement.

"This comes at a time when the ICRC and the Syrian Arab Red Crescent are virtually the only organisations able to work in areas affected by the violence in Syria," said Alexandre Equey, deputy head of the ICRC's delegation in the country.

Britain's Guardian newspaper, meanwhile, reported that Saudi Arabia was set to pay the salaries of the rebel Free Syrian Army, several of whose fighters who defected from the regular army are based in Turkey, to encourage mass defections.

Turkey-Syria relations were already strained by Erdogan's outspoken condemnation of the Assad's government's bloody crackdown that rights activists say has killed more than 15,000 people since March 2011.

The downing of the F-4 is the most serious incident between the two countries since then, but Turkey's Deputy Prime Minister Bulent Arinc played down the tensions.

"We should be calm ... Yes, we accept this is a critical matter but we don't have clear information," he told Anatolia news agency, adding that the results of the ongoing investigation would be publicised "as soon as possible."

In neighbouring Iraq, Foreign Minister Hoshyar Zebari warned that the Syrian crisis might spill over.

"Our main concern is the spillover of the crisis... into neighbouring countries, and no country is immune from this spillover because of the composition of the societies... the connections, the sectarian ethnic dimensions," he told reporters.