JERUSALEM (AP) — Israel accused Iran on Monday of building an airport in southern Lebanon to be used as a launchpad for attacks against Israelis across the border, signaling a possible escalation in tensions between the regional foes.

Speaking at a high-profile security conference hosted by Reichman University near Tel Aviv, Defense Minister Yoav Gallant claimed Iran has been building a runway that slices through forested mountains just 20 kilometers (12 miles) from Israel’s northern border. Gallant displayed satellite photographs that he said showed the site, where the Iranian national flag and the flag of Lebanon’s militant Hezbollah group could be seen.

Gallant alleged that Iran “is planning to act against the citizens of Israel,” using the runway as a base. Iran’s mission to the United Nations did not immediately respond to a request for comment. A spokesperson for Hezbollah declined to comment on Israeli accusations. The defense minister did not specify when the satellite photos were taken.

The location he gave was near the hilly Lebanese city of Jezzin, across the border from the Israeli town of Metulla. Hezbollah earlier this year invited journalists to watch a military exercise in a nearby town in southern Lebanon.

Satellite images from Planet Labs PBC obtained by The Associated Press from July 28 showed work on a 1.2 kilometer (3,937-foot) runway with hangars constructed on a tarmac just east of the runway. Satellite images from January showed the runway largely unpaved. Israel has said in recent years that it shot down Hezbollah or Iranian-linked drones launched from Lebanon and Syria.

Israel and Hezbollah, the Shiite group that controls much of southern Lebanon, fought a war in 2006. The border has remained tense but largely quiet since then, with both sides wary of another major confrontation.

But tensions have mounted. Hezbollah is committed, like its patron Iran, to Israel’s destruction and its leader, Hassan Nasrallah, regularly threatens Israel. In an unusually bold attack earlier this year, a man who Israeli officials said was likely linked to Hezbollah infiltrated into Israel from Lebanon and detonated a bomb that severely wounded an Israeli citizen. The group also allowed Palestinian militant factions to operate in its strongholds and fire rocket barrages toward Israel this past spring.

Israel has complained about further provocations by Hezbollah, including over tents it says the group pitched on the Israeli side of the Blue Line — a demarcation set by the United Nations for the purpose of confirming the Israeli withdrawal from southern Lebanon when it ended an occupation in 2000.

In his speech, Gallant did not describe exactly how Hezbollah would launch attacks from the runway or use the airport for “terrorist purposes.” He said that, in the event of a conflict, Israel would be prepared to strike Hezbollah with “deadly force” to ensure “Hezbollah and Lebanon pay a heavy price.”

Israel considers Iran to be its greatest enemy, and Gallant outlined what he said were a list of Iranian activities along Israel’s various fronts, including support for militant groups in the Gaza Strip and occupied West Bank.

At the same conference, the head of Israel’s Mossad spy agency on Sunday accused Iran of plotting deadly attacks against Israeli and Jewish targets around the world. David Barnea said Israel is prepared to strike perpetrators in “the heart of Tehran.”