Israeli Air Force fighter jets.

An unnamed senior Israeli security official told TIME magazine that Israel destroyed surface-to-surface missiles in a Hezbollah convoy, crossing from Syria into Lebanon on Monday, which were extremely dangerous because of their ability to carry very heavy warheads.

TIME wrote on Wednesday that the “Israeli official indicated they could carry warheads heavier and more dangerous than almost all of the tens of thousands of missiles and rockets Hezbollah now has pointed toward Israel.”

According to TIME, the strike was “the seventh known operation since the Syrian civil war began in 2011 and was an expression of Israel’s only clear policy regarding that deadly conflict: that it will not let Syria’s war become an opportunity for the militant group Hezbollah to improve its anti-Israeli arsenal.”

Israel has warned that it would strike four types of armaments coming into Lebanon: advanced air defense systems, including SA-17 batteries; highly accurate surface-to-surface missiles, such as the Iranian Fateh-110s; long-range land-to-sea missiles, similar to the Russian Yakhont hypersonic anti-ship missile; and chemical weapons. According to TIME, convoys in each of those categories have been targeted by Israel in the past year.

“Our policy is clear,” said Israeli Prime Minister Benjamin Netanyahu on Tuesday, when asked about the overnight strike. “I don’t comment about what we did or didn’t do—but we will do whatever is needed to protect Israel’s security.”

As to the nighttime strike, as the convoy made its way through a mountainous, smuggler’s pass between Syria and Lebanon, the unnamed senior Israeli security official said, “They still think if they’re driving in convoy at night they can’t be seen.”

Lebanese media reported that Hezbollah terrorist Hajji Hassan Mansour, also known as Abu Haitham, who served as a field trainer, died in the strike. In a statement on its website, Hezbollah vowed revenge against Israel.