The Department of Foreign Affairs has been in touch with the family of an Irish-Israeli woman who is unaccounted for in Israel, according to Tánaiste Micheál Martin.
The incident comes after Palestinian militant group Hamas launched attacks across the border from Gaza.
Kim Damti, 22, was at a music event in Re'im in the south of Israel when she was last seen.
Her sister Emily said they have spoken with officials from the Irish Embassy.
In an interview with ABC News, their mother Jennifer Damti said her daughter had phoned them shortly after.
"Kim didn't realise there was like seven or eight Toyota vans full of terrorists and they just shot everywhere," she said.
"They just shot them, slaughtered them like ducks, and that's the reason I'm here, 'cause I want the world to condemn this behaviour.
"I didn't bring my children up to hate anybody.
"You can't sleep. All I can think about is where she is, if she's suffering, if she's still alive. I just want her back.
"So many other mothers here today. I'm not the only one. Everybody is missing somebody."
Mr Martin said his department do not intend to comment specifically on the case at this stage.
"Could I say that, as more information is revealed, I think the full horror of the crimes that were committed yesterday by Hamas are laid bare," he said.
"Hundreds and hundreds of innocent people slaughtered in the most savage of ways."
Taoiseach Leo Varadkar said the Government had no definite detail, but the Irish Embassy on the ground was aware of it.
"We don't have any definite detail beyond that, but certainly we're aware of it and willing to offer any consular assistance we can to any Irish citizens or any dual Irish citizens that are caught up in these terrible attacks," he said.
Mr Varadkar added that the attack by Hamas is "probably the worst attack that Israel has had to endure for 40 years now".
He said the embassy was willing to offer assistance to any Irish or dual citizens caught up in the attacks.
A spokesperson for the Department of Foreign Affairs said that it is in contact with a "small number" of Irish citizens currently in Gaza.
It urged all citizens to avoid all travel to southern Israel, and said people in both Israel and occupied Palestinian territory should "exercise extreme caution".
This advice extended to east Jerusalem.
In a statement to RTÉ's Morning Ireland, it said that those travelling in and out of Ben Gurion airport should keep in touch with their airlines for updates.
"This is a developing situation, with the potential for escalation," the Department said.
"Any citizen currently in Israel or the occupied Palestinian territory, should register with the Embassy."
Mr Varadkar condemned what he described as an "appalling" surprise attack by Hamas and called for an end to hostilities.
He called for the fighting to stop "immediately" and said that Ireland condemns the attacks on civilians "unequivocally".
"The firing of rockets by Hamas and the loss of life in fighting is appalling, as is the impact on people going about their daily lives." he said on X.
Mr Martin urged all involved to "de-escalate" the situation as soon as possible.
Speaking to RTÉ News at a Fianna Fáil event in Dublin city, he said what happened was "shocking".
Mr Martin said the attack was "clearly in breach of international law" and that Israel has the "right to self defence".
However, he said this must be done in a "proportionate way" and that "I fear for the people of Gaza".
"It's important that the voice of moderation emerges in all of this. It's important we do not endure any further loss of life," he said.
Mr Martin also said his department has "activated an emergency response team" to help Irish citizens in Israel, and that in addition to a travel warning has said any Irish citizen in Israel should contact the Irish embassy.
The Department of Foreign Affairs said that it is "closely monitoring situation in Israel & the occupied Palestinian territory" through its embassy in Tel Aviv and its Representative Office in Ramallah.
"Our HQ team are providing support to Irish citizens. Anyone with concerns can contact DFA on 01-4082000," the statement said.
"We urge Irish citizens in Israel and the occupied Palestinian territory to follow the advice of our embassy."
It added that Irish citizens should avoid non-essential travel and register with embassy.
Additional reporting: Gavin O'Callaghan
