Two Catholic churches in Northern Ireland have been targeted with graffiti bearing a message opposed to abortion, ahead of a key referendum in the Republic of Ireland.

Between the late hours of April 22 and the early morning of April 23, a vandal painted on St. Patrick's Cathedral in Armagh a slogan "Save the 8th. Save Ireland." The Eighth Amendment protects unborn children under the republic's constitution and could be repealed in a May 25 vote.

Another slogan was tagged on St. Columcille's Church in Carrickmore in County Tyrone sometime between April 23 and April 24. It appeared to say the traditionally Protestant Democratic Unionist Party's stand against abortion would benefit the unborn who will play in the Gaelic Athletics Association and those who will speak the Irish language, the promotion of which is a subject of controversy among DUP members.

"Only DUP speaks for Irish unborn to speak Irish and play GAA vote DUP," the slogan said, according to the Belfast Telegraph.

Police are investigating criminal damage at both churches.

Sinn Fein, a nationalist party with significant Catholic support, has endorsed the repeal effort in the Republic of Ireland, which would legalize abortion up to 12 weeks into pregnancy. Its party has endorsed legalized abortion in cases of rape, fetal abnormality, and where a woman's mental or physical health faces serious threat, the Irish Times reports.

Garath Keating, a Sinn Fein counselor, said he was "absolutely horrified" at the graffiti in Armagh. He suggested that anyone who objected to Sinn Fein's stance on the abortion referendum should "protest at our office or in a public forum, not write it on a church wall."

"I can't comprehend how anybody could think this is a useful way to convey their point of view," Keating continued. "There is plenty of opportunity and forums for public discussion in respect of any of the matters, but to take to spreading your message by writing on a place of worship is horrifying and despicable."

Thomas Buchanan, a DUP member of the Legislative Assembly, said, "there are strong feelings among members of the community about Sinn Fein's policy on abortion, however that does not excuse anyone engaging in criminal damage."

"It is totally wrong and inappropriate to smear a place of worship, or any public building, with graffiti to make any sort of political point," he said, according to BBC News.

Another Sinn Fein candidate, Órfhlaith Begley, said the incident was "blatant sectarian vandalism" and a "sectarian hate crime."

Pro-abortion rights campaigners have also acted at churches. In the grotto of the Mary Immaculate Church in Inchicore, Dublin, some activists placed upon the altar a sweater bearing the phrase "Repeal." They took a photo and shared it on social media.

Abortion advocacy is also underway in Northern Ireland, which has its own laws. The Department of Health on April 25 released a new report advocating abortion in cases where the unborn child has physical abnormalities.

"Women and babies in Northern Ireland do not need abortion. What women really need is access to holistic, life-affirming and compassionate healthcare that cares for both lives when faced with a difficult prenatal diagnosis," said Bernadette Smyth, spokesperson for Northern Ireland's leading pro-life group, Precious Life.