Argentina's lower house of Congress approved a bill to legalize abortion in the early hours of Friday morning, a big step forward for the legislation that could set the tone for a wider shift in conservative Latin America.

The draft law, which would allow the legal termination of pregnancies up to the 14th week, was passed with 131 votes in favor, 117 against and six abstentions. It will now move up to the Senate, where an even tighter vote is expected.

Supporters of the legislation, dressed in distinctive green scarves, cheered and hugged each other in the streets of Buenos Aires after the vote for the bill, which was backed by the government.

Some of the opponents - who had also marched outside Congress through a mammoth debate on Thursday and stayed out all night for the decision - were in tears.

The votes in Argentina, the birthplace of Pope Francis, come amid calls for greater reproductive rights for women across the predominantly Roman Catholic region.

"This is a fundamental step and recognition of a long struggle that women's movements have been carrying out in our country for years," Elizabeth Gómez Alcorta, the government's Women, Gender and Diversity minister, said after the vote.

"We are going to continue working so that the voluntary termination of pregnancy becomes law."

A similar vote to legalize abortion was narrowly defeated in a Senate vote in 2018 after passing the lower house.

Groups opposing the legislation wore light blue scarves as they marched.

"They don't want to show what an abortion is," said Mariana Ledger who was holding a cross and a dummy of a headless and bloodied fetus. "This is it, and they don't want to show it. They are hiding the truth, we are not foolish people."

Amnesty International welcomed the lower house vote and called on the Senate not to "turn its back" on women.

The initiative includes a parallel bill - which will face a separate vote - to assist women who want to continue with their pregnancy and face severe economic or social difficulties.

Argentine law currently only allows abortions when there is a serious risk to the mother or in the event of rape. Activists say, even in those cases, many women often do not receive adequate care.

Carlina Ciak, a 46-year-old pediatrician who stayed in the square outside Congress until after midnight, said the bill would help women from the most vulnerable groups who were often forced to seek dangerous illegal abortions.

"Abortion as a medical practice exists, even when illegal it never stopped being performed," the mother-of-two said.

The most affected women were from groups already suffering from "misery, poverty, criminalization and all kinds of violence."

"For them, and for our daughters, we will fight until it becomes law," she said.