Syria called an alleged Israeli strike on a military research facility in Damascus a “declaration of war” on Sunday and vowed to retaliate.
Israel has not taken responsibility for the attack.
“We do not comment on these reports at all,” an Israeli military spokesperson said.
The Sunday morning attack is the second alleged Israeli strike in three days. Israeli air forces are believed to have struck at missiles being transferred to Hezbollah Islamist militants on the night of Thursday to Friday.
President Obama defended Israel's right to bomb targets inside Syria without confirming the strike itself.
“I'll let the Israeli government … confirm or deny whatever strikes that they've taken,” Obama told Telemundo in an interview scheduled to run Sunday. “What I have said in the past and … I continue to believe is that the Israelis justifiably ... have to guard against the transfer of advanced weaponry to terrorist organizations like Hezbollah.”