Iran directly threatened Israel on Tuesday following an airstrike on a Syrian air force base Monday that killed at least seven Iranian advisers. Israel is taking the Iranian threats very seriously: The northern border is on high alert amid concerns of a possible revenge attack by Iran or Hezbollah, as well as a possible U.S. strike against the Assad regime in retaliation to the chemical attack at Douma.

>> This is not a drill: Syria showdown could spark Israeli-Iranian and U.S.-Russian clashes ■ Revenge by Iran could push Israel to terminate its Syrian presence

The airstrike, which Iran, Syria and Russia all blame on Israel, targeted Syria’s T-4 airbase near Homs. According to foreign media reports, the strike damaged various capabilities that the Iranians had begun to deploy at the base. Israel has not claimed responsibility for the strike.

The T-4 airbase is one of the key sites where the Iranian Revolutionary Guards’ Quds force is deployed in Syria. According to Arab media reports, the fatalities included a Revolutionary Guards colonel who was responsible for Iran’s drone operations in Syria.

>> Russia's tough rhetoric shows Israel is losing its leeway with the Kremlin ■ Russia vetoes U.S. bid for probe of Syria chemical attacks ■ U.S. strike on Syria could trigger direct military clash with Russia

Open gallery view The T-4 base, near Palmyra, that was attacked. Credit: Google / DigitalGlobe

The strike also apparently killed or wounded other officers and damaged other armaments aside from the drones. The armaments in question could have reduced the Israel Air Force’s freedom of operation in Syrian airspace.

Ali Akbar Velayati, an adviser to Iran’s supreme leader, Ayatollah Ali Khamenei, said in interview with the Hezbollah-affiliated Lebanese television station Al Mayadeen on Tuesday that “Israel’s crime won’t go unanswered.”

Syria and Russia also issued statements denouncing the strike, and the Russian Foreign Ministry summoned Israel’s ambassador in Moscow.

“I don’t know who attacked in Syria,” said Defense Minister Avigdor Lieberman during a visit to the Golan Heights town of Katzrin on Tuesday morning. “But I know one thing for certain: We will not allow Iran to set up shop in Syria, regardless of the cost.”

This is far from the first time Israel has warned that it would see a transfer of Iranian military assets to Syria or the establishment of Iranian military sites there as a “red line” which it will act to enforce.

On Wednesday, the security cabinet met to discuss the tension on the northern border. At the meeting, the intelligence agencies gave the ministers their assessments of recent developments.

The Israeli army is also preparing for another day of Palestinian demonstrations near Israel’s border with the Gaza Strip. But it is also making efforts, with Egyptian help, to calm the mood in the Strip.

On Tuesday, the army announced that it would expand the fishing zone for boats from Gaza. This is one of the steps that senior Hamas officials recently said could help to ease the tension.

For the defense establishment, Gaza is evidently a lower priority than events in the north. If the violence in Gaza continues, the army is liable to further escalate its response in an effort to convince Hamas that it won’t allow a war of attrition along the border. That is also one of the reasons why the air force bombed a Hamas military target in Gaza earlier this week after Palestinians planted improvised explosive devices near the border.