Syria warned on Thursday of a possible “surprise” response to Israel’s attack on its territory and Russia condemned the air strike as an unprovoked violation of international law.

Damascus could take “a surprise decision to respond to the aggression of the Israeli warplanes”, Syrian ambassador to Lebanon Ali Abdul-Karim Ali said a day after Israel struck against Syria.

“Syria is engaged in defending its sovereignty and its land,” Ali told a website of the Lebanese militant group Hezbollah. Syria and Israel have fought several wars and in 2007 Israeli jets bombed a suspected Syrian nuclear site, without a military response from Damascus.

Russia and Iran have strongly condemned the airstrike, though many of the most Western nations publicly opposed to the Assad regime have remained largely silent on the matter. It’s unclear what exactly Syrian President Bashar al-Assad is/isn’t planning in response to the attack, though the involvement of Hezbollah certainly increases fears that the “surprise” in question could be a bombing.