Syria has promised to defend itself "by all available means" following Israeli airstrikes that targeted stockpiles of weapons believed to be on their way to militant groups.

The two Israeli airstrikes in three days heightened tensions in the region, with Syria’s ally Iran and Egypt both condemning the attacks.

While Israeli officials have not confirmed or denied the airstrikes, Israel’s defense department appeared to be preparing for possible retaliation on Sunday. The military deployed two batteries of its Iron Dome rocket defence system in northern cities.

Israeli warplanes launched an airstrike in Syria early Sunday morning targeting a military research facility – the second attack in three days. The facility was reportedly storing Iranian-made missiles believed to be on their way to Hezbollah militants in neighbouring Lebanon.

An intelligence official confirmed to The Associated Press that Israel launched the attack and targeted Fateh-110 missiles, which have precision guidance systems.

An earlier attack on Friday, confirmed by U.S. officials, was also reportedly directed at a weapons warehouse.

Syria’s information minister called the weekend attacks a “flagrant violation of international law” and warned that the country has the right to defend itself “by all available means.”

Following Sunday's early-morning strike, Syria’s Deputy Foreign Minister told CNN the attack is a “declaration of war.”

“When they attack, this is a declaration of war. This is not something that is (new)," Faisal al Mekdad said. "We dealt with this on several occasions, and we retaliated the way we wanted, and the retaliation was always painful to Israel, and they will suffer again."

In a letter sent to the United Nations and the UN Security Council, Syria’s foreign minister said the attack killed and wounded several people and caused widespread destruction.

An amateur video said to be shot early Sunday in the Damascus area showed an enormous ball of fire lighting up the night sky. The video could not be independently confirmed but its contents match reports of the incident in the same area, about 15 kilometres from the Lebanon border.

Damascus-based activist Susan Ahmed said the explosions occurred around 2 a.m. local time, and sent mounds of smoke into the sky.

“Columns of smoke could be seen like mountains,” Ahmed told CTV News Channel on Sunday.

“Here in Damascus, people are really afraid today,” she said. “They’re pretty careful when they’re leaving home.”

Canada, Middle East react to airstrikes

The airstrikes come as Washington considers how to respond to reports that the Syrian regime may have used chemical weapons against its own people.

U.S. President Barack Obama has described the use of such weapons as a "red line," and last week said administration is weighing its options -- including possible military action.

Meanwhile, Canada’s Foreign Affairs Minister John Baird said Sunday the government has “solid evidence” that some chemical weapons were used in Syria, citing intelligence from U.S. and Israeli allies.

“We don’t have specific evidence as to who used them, though we strongly suspect it was the regime,” Baird told CTV’s Question Period.

He added: “We’ll get the facts first before we rush to any conclusions and decision as to how to respond.”

However, Baird maintained that the government remains opposed to arming the rebels – something the U.S. recently confirmed it is considering.

“We are increasingly alarmed by the amount of radical jihadist who are making it into Syria and infesting part of the opposition,” Baird said. “This causes us great concern.”

In the Middle East, both Egypt and Iran condemned the weekend attacks.

Egyptian President Mohamed Morsi called the airstrikes a violation of international law while Iran’s Foreign Minister Ramin Mehmanparast, urged other countries to remain united against Israel.

University of Quebec sociology professor Rachad Antonius said despite Syria’s promises, it is unlikely the country will retaliate.

“The difference in power between Syria and Israel, whether there is or there isn’t a war, is huge,” Antonius told CTV News Channel. “Syria is not in a position to counter attack.”

Israel has said it wants to stay out of the two-year-long Syrian civil war, but Prime Minister Benjamin Netanyahu has repeatedly stated the Jewish state would be prepared to take military action to prevent sophisticated weapons from flowing from Syria to Hezbollah or other extremist groups.

However, Antonius said the airstrikes could be considered an “unprovoked attack.”

“The government of Syria has not attacked, in any way, Israel recently. And Hezbollah did not attack Israel recently either,” he said. “Had it been the other way around…all the countries in the West would consider this an act of war.”

With files from The Associated Press