The Tánaiste Eamon Gilmore has said
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Ms Higgins visited the elderly peace activist in Limerick jail last weekend. Margaretta D'Arcy was jailed for refusing to sign a bond to stay away from unauthorised areas of Shannon airport.
The 79-year-old, who is undergoing treatment for cancer, is serving a three-month sentence for illegal incursion on the runway at Shannon Airport in October 2012.
Ms D'Arcy - a writer and a peace-activist - was protesting against the use of Shannon by the US military.
Mr Gilmore said he hoped Ms D'Arcy's legal team would work on her behalf to secure her release as soon as possible.
He said he did not know about the visit until he read about it in the media.