DAMASCUS, Syria (AP) — Israel carried out a wave of heavy airstrikes across Syria as its troops advanced deeper into the country, a Syrian opposition war monitor said Tuesday, and the Israeli defense minister announced that his forces had destroyed Syria’s navy.

Israel acknowledged pushing into a buffer zone inside Syria following the overthrow of President Bashar Assad. But it remained unclear if Israeli soldiers had gone beyond that area, which was established more than 50 years ago. Israel denied that it was advancing on the Syrian capital of Damascus.

The Israeli military said Tuesday that it carried out more than 350 strikes in Syria over the last 48 hours, hitting “most of the strategic weapons stockpiles” in the country to stop them from falling into the hands of extremists.

The targets included air defense systems, military airfields, missile depots and dozens of weapons production sites in Damascus and other cities. Associated Press reporters in the capital heard heavy airstrikes overnight and into Tuesday morning.

Israeli missile ships also simultaneously struck two Syrian navy facilities, where the military said 15 Syrian naval vessels were docked. Israel did not specify how many vessels it struck, but the private security firm Ambrey said it had seen evidence that at least six Soviet-era missile ships were hit.

Israeli Defense Minister Israel Katz said Israel intended to establish a demilitarized zone in southern Syria.

Speaking at a navy base in Haifa, Katz said the army will create a “defense zone free of weapons and terrorist threats in southern Syria, without a permanent Israeli presence, in order to prevent terrorism in Syria from taking root.”

He gave few details on what that entailed, but warned Syria’s rebels that “whoever follows Assad’s path will end up like Assad. We will not allow an extremist Islamic terrorist entity to act against Israel.” Israel has also long warned that the Syria-Lebanon border could be used to smuggle weapons to Hezbollah militants.