Streets surrounding the Irish parliament were shut down and traffic ground to a halt during rush-hour as around 2,000 demonstrators staged a spontaneous protest, in support of a young pregnant women who died when doctors refused her an abortion.
Kildare Street and Molesworth Street were flooded with protesters who listened to speeches from pro-choice campaigners, before sitting down for a minute's silence.
Elsewhere, supporters in Cork held a candlelight vigil at the city's Opera House in memory of Savita Halappanavar.
The Irish Government has come under heightened pressure to reform complex abortion laws after the death of a Ms Halappanavar in Galway University Hospital.
Mrs Halappanavar, a 31-year-old dentist, was 17 weeks pregnant when she died on October 28 after suffering a miscarriage and septicaemia.
Her husband, Praveen, has alleged that doctors refused several requests for a medical termination because the foetus's heartbeat was present.
Mr Halappanavar has claimed that following his late wife's appeals, they were told: "This is a Catholic country."
Choice Ireland's Stephanie Lord said the same questions were still being asked after 20 years.
"If a woman is pregnant, her life in jeopardy, can she even establish whether or not she has a right to a termination here in Ireland? There is still a disturbing lack of clarity around this issue," she said.
Dr Ruth Cullen, of the Pro Life Campaign, said some people in favour of allowing abortion were exploiting Ms Halappanavar's tragic death.
"The Medical Council Guidelines are very clear that all necessary medical treatment must be given to women in pregnancy," she said.