The Israeli military have crossed “yet another line”, the Taoiseach has said.
Simon Harris said he is “extraordinarily concerned” about the escalating conflict in southern Lebanon.
The Fine Gael leader accused Israel of “flouting” international law by its “disproportionate actions”.
On Saturday, it was reported by the United Nations that another peacekeeper was injured by gunfire in southern Lebanon.
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The peacekeeper at the United Nations Interim Force in Lebanon (Unifil) headquarters in Naqoura was hit by gunfire on Friday following ongoing military activity in the area.
Unifil said it could not confirm the origin of the gunfire.
Speaking before the Unifil statement was released on Saturday, Mr Harris said: “I’m extraordinarily concerned about the situation that we see in southern Lebanon.
“I think we have seen yet another line crossed by Israel. Peacekeepers and peacekeeping is protected by international law.
“In my view, we have already seen Israel flout international law on many occasions, particularly in terms of their disproportionate actions, and the impact that that has had on children and on civilians in Gaza.
“Now we’re seeing international law being flouted in relation to peacekeepers and peacekeeping. All the time, while this is going on, other facts are being somewhat overlooked or overshadowed, really important facts, like the fact around food.
“The fact that the World Food Programme (WFP) has not been able to get food supplies into northern Gaza. These are extraordinarily serious situations as we head into a winter period.”
Mr Harris will travel to Brussels for the European Council on Thursday, where he said he will urge his European counterparts to “speak out” on issues in Gaza and Lebanon.
He said he wants to see the EU-Israel Trade Agreement reviewed.
Mr Harris also said that the current advice for Irish peacekeepers is to continue it Unifil mission, but added that it was a “very dangerous situation”.
In a post on social media site, X, formerly Twitter, the Defence Forces said all its personnel deployed with Unifil are well and accounted for and that no Irish personnel were involved in the latest incident.
“Our personnel continue to adhere to all necessary force protection and risk mitigation measures,” it added.
Earlier this week, Israeli troops fired on UN headquarters in southern Lebanon, injuring two peacekeepers for the second time in as many days.
Mr Harris discussed the Israeli activity on the Blue Line (demarcation line in Lebanon) with US President Joe Biden in the Oval Office on Wednesday.
He said the leaders agreed that the Blue Helmets (UN peacekeepers) must “always be afforded full protection”.
The Taoiseach has also been communicating with UN secretary-general Antonio Guterres.
In a statement, Mr Harris said: “Israel must stop firing on UN peacekeepers serving with Unifil in Lebanon.
“Israel must listen to the voice and the concerns of the international community.”
Mr Harris said he will be discussing the incidents with EU colleagues at next week’s meeting of the European Council.
“I will be calling for an immediate ceasefire that can allow us to focus on implementation of UN Resolution 1701 and get people back to their homes,” he added.
Meanwhile, Tanaiste Micheal Martin called on the international community to pressure Israel to stop its “reckless and intimidatory” activity.
Mr Martin said there had been a “serious intensification of IDF (Israel Defence Forces) hostility towards UN forces”.
The Chief of Staff of the Irish Defence Forces said Israel has to be accountable for “deliberate” and “direct fire” on UN outposts.
Lieutenant General Sean Clancy said the attacks were a “clear and egregious” violation.
“A round of a tank into an observer tower, which is a very small target, has to be very deliberate, and it is a direct fire.
“So from a military perspective, this is not an accidental act, it is a direct act.”