Hezbollah said on Saturday its field commanders were ready to respond to an attack a week ago that the Lebanese group blamed on Israeli drones, after Israel's military ordered extra forces to deploy near ceasefire line.
Tensions have heightened between the Iran-backed Lebanese movement and its old enemy Israel - who fought a month-long war with each other in 2006 - since two drones crashed in the southern suburbs of Beirut that are dominated by Hezbollah.
Hezbollah leader Sayyed Hassan Nasrallah said in a televised speech that all options were open to counter Israeli drones violating Lebanon's sovereignty, Reuters reported.
In his Saturday speech, Nasrallah vowed to retaliate "at all costs" and target Israeli drones, which often operate in Lebanese airspace, AFP said.
"The response will be open... from Lebanon," he said, "in the Shebaa Farms or anywhere on the border".
In 2015 and 2016, Hezbollah targeted Israeli military vehicles in the disputed Shebaa Farms area along the Lebanon-Israel ceasefire line in revenge for Israeli strikes on its fighters in Syria.
In a rare incident on Wednesday, the Lebanese army opened fire on Israeli drones that had violated Lebanon's southern airspace, forcing the aircraft to return back across the border.
Drones like the ones used in the Beirut attack last weekend "open the door to assassinations" if left unanswered, Nasrallah said. "This matter will not be tolerated ... Israel must pay the price."
Israel has accused Iran of stepping up efforts to provide Hezbollah with precision-guided missile production facilities, a warning to Beirut that Israeli counter-strikes may escalate.
Israel's army said on Saturday that in the past week its "ground forces, air, navy and intelligence forces improved their preparedness for various scenarios in the northern command area."
It posted on Twitter footage of tanks and ground forces being deployed.
Without claiming responsibility for the drone attack, the Israeli military has published what it said were details about the Iranian campaign to boost Hezbollah's missile capabilities.
Precision-guided missiles may pose a counter-balance to Israel's overwhelming military force in any future war, with the capacity to home in on and knock out core infrastructure sites.
Nasrallah accused Israeli Prime Minister Benjamin Netanyahu of seeking a pretext to attack and to change the rules of engagement with Hezbollah.
He denied that Hezbollah had factories to produce the weapons. Still, he said: "We have as many precision-guided missiles in Lebanon as we need for any confrontation, small or big."
A new conflict between the two adversaries would destabilize a Middle East already fraught with tensions between the United States and Iran.
Iranian Foreign Minister Mohammad Javad Zarif accused the US on Twitter of engaging in "piracy and threats" to stop Tehran selling oil to clients, after Washington blacklisted an Iranian oil tanker it said was headed to Syria.
Washington has also ratcheted up sanctions against Tehran in a row over Iran's nuclear ambitions.
Israel is concerned about the growing regional influence of Iran and its militia allies, including Hezbollah, in countries like Syria and Iraq.
Shia militias in Iraq, many of which are backed by Iran, blame recent blasts at their weapons depots on the US and Israel.
Politics is also playing a role, as Netanyahu seeks to appear decisive ahead of an election in three weeks.
Netanyahu on Tuesday warned Nasrallah to "be careful" with his words and actions.
Directing his words at Nasrallah, Netanyahu said in a speech "he knows very well that the state of Israel knows how to defend itself well, and to repay its enemies".
On Saturday, Nasrallah said he wanted "the enemy to remain confused, as it is now."
The Hezbollah leader did not spell out the timing of any retaliation, but he said it "is now in the hands of the field commanders who know what they must do ... and what the limits are."
Hezbollah, which was founded by Iran's elite Revolutionary Guards in 1982, fought its last war with Israel in 2006 after it captured two Israeli soldiers in a cross-border raid.
Almost 1,200 Lebanese, mostly civilians, and 158 Israelis, mostly soldiers, were killed in the conflict.
