Hezbollah has a factory for making precision missiles in southern Lebanon built with Iranian help, the Israeli military has claimed.
The site is allegedly in Lebanon’s Bekaa Valley and the Shiite militia has moved crucial material from the site to "civilian locations" in Beirut for fear of strikes, Israel's military said.
Israeli forces also published images of the site's alleged location.
There was no immediate Hezbollah response to the claim, which came just days after heightened tension between the two foes.
Hezbollah and Israel, which technically remain at war, traded fire for the first time in years last week.
Hezbollah launched anti-tank missiles at an Israeli armoured vehicle near the border, causing no casualties. Israel retaliated with artillery fire into southern Lebanon.
The Lebanese movement said the attack was retaliation for an Israeli air strike near Damascus last month that killed two of its members. Israel said its actions thwarted an Iranian-orchestrated drone attack squad.
Hezbollah accused Israel of sending two attack drones into southern Beirut days before the strike. Both of those drones crashed.
Israel has not formally claimed responsibility for the Beirut drone strike, which a regional security source said hit a component of the missile project.
Hoping to push Beirut into reining in Hezbollah, Israel signalled that in any further flare-up it could carry out widespread attacks on Lebanon.
Israel recently expressed concerns that Hezbollah and Iran are pursuing a missile-production industry in Lebanon. On Saturday, Hezbollah leader Hassan Nasrallah denied Israeli claims and said that the Iranian proxy group did not "have factories to produce precision-guided missiles in Lebanon".
A Hezbollah source told Lebanese newspaper The Daily Star that there was "no confirmation or denial" of Israeli claim.
“Israel is always looking for any victory or any piece of information,” the source said.
Lebanese Prime Minister Saad Hariri said on Wednesday that the country remained committed to the UN Security Council resolution that ended the one-month war between Israel and Hezbollah in 2006.
"What matters to us is to continue to implement this resolution and protect Lebanon," he said.
"The Lebanese state contained what happened diplomatically, starting with the drones, to Hezbollah’s reaction.
"We should preserve stability and UNSCR 1701. The main problem is that the situation in the whole region is tense, and we do not need new crises. This is the basis and Lebanon’s protection is the key."
Neither side appears to seek a full-blown conflict. But both seek to maintain its deterrence through strength. After the exchange of fire on the Lebanese-Israeli border at the weekend, Nasrallah threatened to hit "deep inside" Israel and he said there were "no more red lines" in Hezbollah's confrontation with Israel.
After the flare-up, Mr Hariri contacted senior US and French officials to urge their countries and the international community to intervene.
The UN called for restraint and France said it had made "multiple contacts" to avert further fire.
The US slammed the "destabilising role" of Iranian allies in the Middle East and said it "fully supports Israel's right to self-defence".
