Concern about the possibility of broader war in the Middle East grew Monday after reported airstrikes on Syrian military installations.
The reported strikes killed 42 Syrian soldiers, the opposition Syrian Observatory for Human Rights said Monday, citing medical sources. It said 100 people remained missing.
The Syrian government warned Sunday's apparent strikes -- which followed one last week that Syria also blames on Israel -- "opens the door wide for all the possibilities."
Syrian ally Iran warned of a "crushing response" while Russia called reports of Israeli involvement "very worrying."
But an Israeli general who commands forces on the Syrian border said "there are no winds of war," according to the Israel Defense Forces website.
The heightened tensions come amid questions over possible chemical weapon use in Syria and international debate over how to respond to the country's bloody civil war, in which more than 70,000 people have died in more than two years of fighting.
On Monday, a U.N. official spoke of strong suspicions that rebels, not Syrian government forces, have used chemical weapons.
Details of reported strikes
Syria claimed Israeli missiles struck at its military facilities on Sunday.
According to the state-run SANA news agency, Israeli missiles struck a research center in Jamraya, a facility in Maysaloun and what the news agency described as a "paragliding airport" near Damascus.
"The Israeli terrorist aggressions on the Syrian territories have left no room for hesitation, weakness, self-dissociation or silence as Syria would not forgive us all if we hesitated in defending it," SANA reported Syrian Prime Minister Wael al-Halqi as saying.
The blasts prompted terrified residents nearby to run for cover.
"Everything kept exploding over and over again," said Anna Deeb, whose family lives just over a mile away. "We could hear gunshots, we could hear people screaming. ... We didn't know what to do, and there was a problem with us breathing because the smoke was too much."
Syria says the attack followed another Israeli airstrike late last week.
Israel has not confirmed or denied that its forces were involved in any attacks inside Syria, but a U.S. official told CNN's Barbara Starr on Monday that Israeli forces conducted Sunday's strike, as well as one last week.
Sunday's strike targeted a research facility in a mountainous area near Damascus and weapons that were to be transferred to Hezbollah, according to the source.
The earlier strike, which U.S. officials had previously said happened Thursday or Friday, targeted Fateh 110 missiles stored at the Damascus airport, the source said.
SANA reported that the allegation of weapons transfers was false.
And Syrian Deputy Foreign Minister Faisal al-Mekdad told CNN the attacks amount to a declaration of war by Israel.
"The details are not clear on what happened," al-Mekdad told CNN. "Did they fire missiles? ... It is not clear for me, because I don't know how it happened, and of course it is worrying, but Israel will suffer the same."
While Israel has not acknowledged responsibility for the attacks, the country has long said it would target any transfer of weapons to Hezbollah or other terrorist groups.
"We are watching everything when it comes to the movement of these types of weapons. We have the means to do that," a senior Israeli defense official told CNN's Sara Sidner on Sunday. The official is not authorized to speak to the media.
Shaul Mofaz, a lawmaker in Israel's Knesset, told Israeli Army Radio on Sunday that Israel isn't meddling with Syria's civil war. But Israel must protect itself from Lebanese militants, he said.
"For Israel, it is very important that the front group for Iran, which is in Lebanon, needs to be stopped," Mofaz said.