As for who is paying for those ads, said Sheridan, "the only people who know that for certain are Facebook themselves".
The Transparent Referendum Initiative has been tracking online advertising around the vote.
Facebook says it won't accept any foreign ads related to the upcoming abortion referendum in Ireland.
Irish voters will decide on May 25 whether to repeal a constitutional amendment that amounts to a near total ban on abortions, including in cases of rape and incest.
Facebook made the announcement after concerns were raised about organisations based outside Ireland who were trying to influence the outcome of the referendum by buying ads. It will not be able to respond to reports or objections from the public, a spokeswoman said, as it does not yet have automated tools to respond to such communications.
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However, this action did not extend to blocking ads simply because they had been placed by foreign organisations.
The move is a long time coming for some as Facebook has been criticised for its impact on the U.S. presidential election in 2016, and there have been questions raised about it influence over the UK's Brexit vote. We do not intend to block campaigns and advocacy organisations in Ireland from using service providers outside of Ireland. There are now certain circumstances which allow for an abortion, such as if the mother's life is threatened.
"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 understand the sensitivity of this campaign and will be working hard to ensure neutrality at all stages", Facebook stated. Its campaign Co-Director Ailbhe Smyth said: "We view this as a clear recognition by Facebook that external forces with vast resources can have disproportionate yet impactful influence in political campaigns. I think Google and Facebook and all the other social media companies out there will be responsible in relation to this and are facing the consequences that can happen as a result of this", he added. "They were late with Russian interference in the United States election ..."
In April, Facebook announced it would vet ads relating to the UK's local elections, which took place earlier this month.