Syria accused neighboring Israel on Wednesday of conducting an airstrike on what it described as “scientific research centers” northwest of the capital Damascus.

Sources told the Reuters news agency as well as Al Jazeera, the Qatari news organization, that Israeli warplanes bombed a convoy near the Lebanese border carrying anti-aircraft missiles that were made in Russia and supposedly destined for the terrorist group Hezbollah which the Syrian regime has armed and financed in the past.

A statement from Syria’s army command denied that a convoy was the target. It insisted that Israel had “carried out an act of aggression” and killed two people in its attack on the research facility.

Israel and its ally the United States refused to comment on the strike as of Wednesday. As recently as this weekend, Israel warned that it might launch a preemptive strike against Syria if chemical weapons threatened to fall in the hands of Hezbollah or other Islamic terrorist organization.

Violence has raged in Syria for close to two years. Forces loyal to President Bashar al-Assad have been locked in a fierce civil war with mostly Sunni insurgents who control parts of the north and east of the country. Other sectarian groups in Syria, including Alawite Shiites and Christians in the northwestern coastal strip and the larger cities, largely support Assad for fear of a majority Sunni government. Neither side seems able to break the gridlock and force a resolution to the conflict.