Israel has implicitly confirmed it staged an air strike on Syria last week, with President Bashar al-Assad accusing the Jewish state of trying to further destabilise his war-torn country.
The foreign minister of Damascus' ally Iran, meanwhile, said he welcomed Syrian opposition leader Ahmed Moaz al-Khatib's stated readiness to hold talks with representatives of Assad's regime.
Four days after an air raid which Damascus said targeted a military complex near the capital, Israeli Defence Minister Ehud Barak spoke to reporters in Munich on Sunday but refrained from explicitly confirming that Israel staged the strike.
Barak told the Munich Security Conference that the strike was "another proof that when we say something we mean it."
Wednesday's air strike targeted surface-to-air missiles and an adjacent military complex believed to house chemical agents, according to a US official, who spoke on condition of anonymity.
The New York Times, citing a senior US military official, reported Sunday that the air strike may have damaged Syria's main research center on biological and chemical weapons.
Damascus has threatened to retaliate, further fuelling fears of a regional spillover of the country's 22-month conflict which the UN says has already left more than 60,000 people dead.
A fierce critic of both Assad and Israel, Turkish Prime Minister Recep Tayyip Erdogan accused Israel of waging "state terrorism" as he condemned the air strike on Syria as an unacceptable violation of international law.
"We cannot regard a violation of air space as acceptable. What Israel does is completely against international law... it is beyond condemnation," Erdogan told reporters.
Syrian ally Algeria also condemned the air strike, calling the action "a violation of international law, foreign aggression and a threat to state sovereignty and territorial integrity," in a statement released by the state news agency.
In the wake of the strike, US Defence Secretary Leon Panetta told AFP that Washington was increasingly concerned that Syria's "chaos" could allow Lebanon's powerful Hezbollah movement to obtain sophisticated weapons from Damascus.
Israeli armed forces chief Lieutenant General Benny Gantz on Sunday started a visit to Washington with the Syrian conflict and Iran's controversial nuclear programme on his agenda.
And US Vice President Joe Biden flew to Paris for talks on Monday with President Francois Hollande also covering Syria.
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In Damascus, Assad accused Israel of seeking to "destabilise" Syria, state news agency SANA reported.
The raid "unmasked the true role Israel is playing, in collaboration with foreign enemy forces and their agents on Syrian soil," he told Saeed Jalili, who heads Iran's Supreme National Security Council.
Amid the insecurity, Israeli security sources said the Jewish state has plans for a buffer zone inside the Syrian border to prevent radical groups from approaching its territory.
"There's a plan in the military's northern command for the 'day after' according to which, when Bashar Assad is no longer president of Syria, there's a fear that terror elements will try to approach the fence," one source told AFP.
On the political front, key Damascus and Hezbollah backer Tehran also said on Sunday that it welcomed opposition chief Khatib's overture for talks with regime representatives.
"It's a good step forward," Foreign Minister Ali Akbar Salehi said at the Munich Security Conference, where he said he had held a "very good meeting" with Khatib.
Iran has joined UN Security Council members Russia and China in consistently backing Assad's regime throughout the almost two year-long conflict which has also forced more than 700,000 people to flee Syria.
After Khatib met Iranian and Russian representatives in Munich, opposition spokesman Walid al-Bunni told AFP by telephone that Moscow must now pressure Assad to end the spiralling conflict.
"The ball is now in Russia's court," the Syrian National Coalition's Bunni said, although he conceded that there has been "no breakthrough in Russia's stance."
On the ground, at least 16 people, among them 10 children and a rebel commander, were killed in a missile attack by the army on Sunday on a rebel-held area of the northern city of Aleppo, according to the Syrian Observatory for Human Rights.
Video distributed by activists showed a man describing the carnage. "I saw a 13-year-old's body sprawled on the ground, I saw mutilated body parts everywhere," he told the amateur cameraman.
The Britain-based watchdog, which relies on a network of activists and medics for its information, said at least 125 people were killed in violence across Syria on Sunday, among them 58 rebel fighters.