Israel’s military has been put on high alert amid heightened tensions along the northern border and with Iran threatening to avenge an airstrike on a Syrian air base believed to have killed at least 14 people, including 7 Iranian military personnel.

Russia, Syria, Iran and the United States have all said Israel carried out the predawn Monday missile barrage on the T-4 Air Base near Palmyra in central Syria. Israeli officials refused to comment on the strike.

On Tuesday, a top adviser to Iran’s Supreme Leader Ayatollah Ali Khamenei threatened Israel.

“The crimes will not remain unanswered,” Ali Akbar Velayati said during a visit to Syria, according to the official Islamic Republic News Agency.

Iran’s Foreign Ministry also accused Israel of “flagrant” aggression in Syria following the attack.

Israeli officials did not appear to be taking the threat of a retaliatory attack lightly — either by Iran, or its proxy, the Hezbollah terrorist group.

On Tuesday, Defense Minister Avigdor Liberman appeared to allude to the strike, saying that Israel “will not allow Iranian entrenchment in Syria. Whatever the cost.”

Read more at Times of Israel