Savita Halappanavar, a 31-year-old dentist, was 17 weeks pregnant when she died in Galway University Hospital last month from septicaemia brought on by a miscarriage.
Her husband Praveen had claimed his wife pleaded with doctors to perform a medical termination, but they denied her requests because the baby's heartbeat was present.
He further claims the couple were told: "This is a Catholic country."
The protest in Belfast city centre came a day after 2,000 people gathered outside the Dáil in Dublin to demand Government reform of abortion laws in the Republic of Ireland.
To deny women a choice fails to recognise medical and societal realities. Government must not fail society on this issue and must take appropriate action.
Aisling Gallagher, NUS-USI
Activist Virginia Santini told UTV that call was being echoed north of the border.
"Tonight really is to show our anger and to show our support for our fellow pro-choice activists in the South who are also campaigning on this issue and to say that we need change," she said.
"We need abortion reform and we also need clarity on the Health Minister regarding when an abortion can be given in terms when it could save a woman's life."
Authorities in the Republic have launched two investigations into Ms Halappanavar's death, which has reignited the debate on both sides of the border as to when a termination can be carried out.
Current laws in both jurisdictions only permit abortions to go ahead if the mother's life is at risk or if there's a serious threat to her long-term health.
But calls have been made for greater clarity when it comes to the guidelines.
Stormont Health Minister Edwin Poots says he is currently taking advice and will issue guidelines on the termination of pregnancies in Northern Ireland. A date has yet to be set for their release.
I want to give the family certainty as quickly as possible and not left in limbo for a moment longer than necessary. I want the findings of this to stand up to the scrutiny of the world.
Dr James Reilly, Irish Minister for Health
Meanwhile, the Master of the National Maternity Hospital in Dublin has said it's unclear in the Republic exactly when doctors can sanction an abortion.
"The area of difficulty really is in the grey areas, where we are not quite sure of outcome of the certain disorder or the disease, we are dealing with probabilities, we are dealing with potentials," Rhona Mahoney told UTV.
"So we are not dealing with certainty and that's the difficulty we have."
The issue of abortion has already been making the headlines in Northern Ireland, with the opening of a Marie Stopes sexual health clinic - which offers a range of services, including medical abortions.
The abortions must comply with current laws and are therefore only carried out when authorised by two doctors on the grounds that the mother's physical or mental health is at serious risk.
They would also only be carried out during the first nine weeks of pregnancy.
The pro-life organisation Precious Life, which was protesting outside the Marie Stopes clinic, told UTV the tragic death in Galway should not be used as a platform for change.
People may be angry, but my question is why are people angry - when the law in Ireland protects mothers and babies?
Bernie Smyth, Precious Life
"What would concern me is that people would be using this case as a vehicle to legislate on abortion," Bernie Smyth, from the organisation, said.
"It is very important that we look at all the facts and it is very important that we let the investigation be heard."
Meanwhile, Ms Halappanavar's mother - who lives in India - spoke out against the hospital staff who were treating her daughter.
"The authorities there should have considered the fact that we follow the Hindu faith and they should have taken a decision after taking everything into perspective," she said.
As well as outside the Dáil, a protest was also held on Wednesday outside the Irish Embassy in London.
Further demonstrations are now expected to take place in Cork and Londonderry, while a march and candlelight vigil have also been planned for Dublin at 4pm on Saturday 17 November - to coincide with a candlelit vigil in Galway, where Ms Halappanavar lived and died.