Syria's state news agency says Israeli rockets have hit a miitary research facility on the outskirts of Damascus.

If confirmed, it would be the second strike on targets in Syria in three days - and signal a sharp escalation of Israel's involvement in the country's civil war.

Israel says an airstrike on Friday and another in January were aimed at weapons shipments bound for the Lebanese Hezbollah militia.

US President Barack Obama says Israel is right to protect itself.