DAMASCUS, Syria ( TheStreet) -- Explosions reportedly rocked the outskirts of the Syrian capital early Sunday, and Syria's state news agency said they resulted from Israeli air attacks. If Israel did indeed carry out an airstrike, it would be the second in three days and would mark a heightening of Middle Eastern tensions as Syria's civil war escalates. Syria's Sana news agency reported that Israeli jets were targeting the Jamraya research center Sunday morning. Earlier Israeli attacks this year -- one overnight Thursday and one in January -- were near the same research center. On Saturday, U.S. officials said that Thursday's attack was aimed at a shipment of advanced missiles that Syria wanted to transfer to the Hezbollah militant organization, The New York Times reported. As it fights a civil war, the regime of Bashar al-Assad enjoys the support of both Iran and Lebanon's Hezbollah. The regime has been shipping weapons from Iran to Hezbollah, but as the civil war escalates, al-Assad may want to speed up weapons shipments to the Lebanese militants before he loses power, the Times also said. Residents of Damascus reached by phone said they heard large explosions after 2 a.m. coming from the Qasioun Mountains that overlook the capital, The Wall Street Journal reported.