However, the move will not prevent ads that are funded from overseas if they are placed through organisations located in Ireland.
The company is also changing its advertising policies, including allowing only authorized groups to buy political ads.
The social media giant said yesterday that it would be putting a block on all advertisements relating to the referendum that come from outside of Ireland.
"Well, it's a start and obviously that's something we have to look at as well in the future in relation to that", Mr Breen said.
"We feel the spirit of this approach is also consistent with the Irish electoral law that prohibits campaigns from accepting foreign donations", it said.
The company said it would rely on reports from established campaign groups on both sides of the campaign to identify foreign-based ads, as its automated election integrity tools are still in development.
Facebook has previously committed to introduce such tools but has said they are not ready in time for the referendum.
Facebook will no longer accept ads from groups outside of Ireland related to the upcoming abortion referendum, the social network announced Tuesday.
The Irish Transparent Referendum Initiative has identified several ads paid for by United Kingdom and US-based anti-abortion groups targeting users in Ireland ahead of the referendum.
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"Our View Ads feature - which enables Irish Facebook users to see all of the ads any advertiser is running on Facebook in Ireland at the same time - has been fast-tracked and is operational".
In a letter made public to all church members last Sunday, the PCI said that "meaningful protection for the unborn can only be secured if the Eighth Amendment is retained in the forthcoming referendum".
The statement goes on to note that the integrity tool will require the advertiser to verify their location.
It pointed out that the company was concerned over foreign attempts to influence the outcome of the referendum.
The ban means that individuals and organisations outside of Ireland can not launch ad campaigns aimed at voters.
Facebook has already stepped up efforts to tackle fake news ahead of the vote, rolling out a new tool in Ireland to give users more information about political advertisements and sponsored posts in their news feeds.
"We understand the sensitivity of this campaign and will be working hard to ensure neutrality at all stages", Facebook stated.
Facebook stated the ban will apply equally to both sides of the debate and that it has "built relationships with political parties, groups representing both sides of the campaign".