Syria vows to retaliate against Israel

A series of massive explosions illuminated the dark sky over Damascus early Sunday, igniting renewed claims that Israel has launched attacks into the war-torn country, cNN reported.

Syria's government said the explosions were the second Israeli airstrike in three days. The latest target, officials said, was a military research facility outside the Syrian capital. A top Syrian official told CNN in an exclusive interview that the attack was a "declaration of war" by Israel.

Syrian authorities vowed to retaliate against Israel but did not specify what action they would take.

The Israeli military would not confirm or deny the Syrian claim that Israel fired rockets that hit the Jamraya research center in the Damascus suburbs.

"We do not comment on these reports at all," an Israeli military representative said.

United Nations Secretary-General Ban Ki-moon expressed "grave concern" over the reports of Israeli airstrikes in Syria Sunday but stressed that the U.N. is not "in a position to independently verify what has occurred," his spokesman said.

Sunday's explosions mark the third time Israel has been accused of striking inside Syria this year.