Sinn Féin leader Mary Lou McDonald has said she is "very concerned" for the safety of those travelling on the Gaza-bound aid flotilla.
It comes as organisers of the flotilla as well as a number of Irish and international pro-Palestinian activists said they heard explosions and saw multiple drones target some of their boats.
Speaking to RTÉ News, Ms McDonald said: "There are more than 20 civilians, Irish citizens on the flotilla, including our colleague Chris Andrews."
"There is no doubt that the Israeli targeting of the flotilla defies international law," she said.
"They are acts of intimidation and menace."
The Global Sumud Flotilla (GSF) departed Barcelona on 31 August, with the aim of breaking Israel's blockade of Gaza. It currently numbers 51 vessels, most of which are off the Greek island of Crete.
It had already been targeted in two suspected drone attacks in Tunisia, where its boat had been anchored before resuming its voyage towards Gaza.
Ms McDonald added it is "absolutely essential that the Irish Government and others confront Netanyahu and confront Israel".
"They believe they can act any way they wish because that has been allowed," she said.
"The security of people on the flotilla needs to be guaranteed."
She said she has been speaking to Senator Andrews and "his concern is for the wider safety of the flotilla and for people in Gaza who are suffering unspeakable horror".
Speaking at a protest outside Leinster House, Ms McDonald said governments needs to show "the red card" to Israel. She said sanctions on the country are "needed now".
"This has gone on too long," said Ms McDonald.
"We face sure catastrophe and the extermination of the Palestinian people."
Senator Andrews, who is on board the ship 'The Sceptre', said it was struck four times by drones.
He said there were no injuries or serious damage inflicted, and that those on board remain undeterred.
Senator Andrews called for the Irish Government to "arrange for an observer vessel to accompany the flotilla to ensure that Israel does not violate the human rights of its participants".
"This is the most serious assault by Israel on this flotilla since it first departed from Barcelona over three weeks ago.
Read more: Italy sends navy assistance after Gaza flotilla attack
"The Irish Government has a responsibility to protect its citizens on this flotilla, as well as to stand up for human rights and justice," he said.
Senator Andrews said the Irish Government needs to "publicly challenge the dangerous and blatantly false attempts by Israel to misrepresent the purpose of this flotilla as anything other than non-violent and humanitarian in nature".
"Ireland needs to stand up to these threats and say clearly to the world that Israel's weapons of war will not deter humanity," he said.
"I urge people at home to contact the Department of Foreign Affairs, the Taoiseach, the Tánaiste, and their local public representatives to call on them to intervene to protect this flotilla."
Lynn Boylan to write to EU commission
Sinn Féin MEP Lynn Boylan said she will write to the EU commission to demand they call for safe passage of the flotilla.
"The EU must not stand idly by while innocent civilians are put in danger by doing what the EU hasn't had the courage to do," the Dublin MEP said.
"I would also urge everyone to contact the Department of Foreign Affairs and urge them to intervene to protect the many Irish citizens, as well as all other civilians travelling as part of this peaceful flotilla," she added.
People Before Profit TD Paul Murphy wrote on X: "The #GlobalSumudFlotilla is under attack from Israel in international waters right now. Multiple boats reporting attacks by drones. Contact the government. Demand they send an observer to the flotilla."
Israel, which blocked two previous attempts by activists to reach Gaza by sea in June and July, said Monday it would not allow the flotilla to reach the embattled Palestinian territory.
Israel has come under huge international pressure over its war in Gaza, which has sparked a dire humanitarian crisis in the Palestinian territory.
Last month, a body backed by the United Nations officially declared famine in part of Gaza.
While on 16 September, UN investigators accused Israel of committing "genocide" in the besieged territory, nearly two years after the war erupted following Hamas's 7 October 2023, attack on Israel.
