Pope Francis has hinted that the Catholic Church could relax its ban on contraception for women at risk of contracting the Zika virus.

The pontiff insisted that abortion remained a crime but said avoiding pregnancy was “not an absolute evil”.

His remarks came in response to a question about how best to tackle the Zika outbreak across Latin America.

The virus has been linked to the microcephaly birth defects in babies, which can cause development problems.

“We must not confuse the evil consisting of avoiding a pregnancy with abortion,” Pope Francis told reporters on a flight returning home from a visit to Mexico.

“Abortion is not a theological problem. It is a human problem, medical. One person is killed to save another. It is evil in itself, it is not a religious evil, it is a human evil,” he said.

“Avoiding a pregnancy is not an absolute evil. In certain cases, as in this one, or in the one I mentioned of Blessed Paul VI, it is clear,” he went on.

The 79-year-old was referring to a predecessor’s decision to authorise nuns at risk of rape in Africa to use contraceptives

The Pope’s comments about avoiding pregnancy in areas where the Zika virus is prevalent are an immensely significant moment. While he does not specifically condone artificial contraception, which is against Roman Catholic teaching, he appears to signal an unexpected openness to the idea if used in order to prevent further infection.

Asked directly whether the Church would consider it permissible to use contraceptives in order to prevent transmission of Zika, Pope Francis said that in some cases the “lesser of two evils” could be applied and spoke of example of Blessed Paul VI, a Pope in the early 1960s who allowed nuns in Africa to use birth control in order to prevent them conceiving children from rape.

That leaves the door open to Catholic families in affected areas to follow their own consciences on the matter. However, the Pope made abundantly clear that abortion remained “a crime, an absolute evil,” while birth control was not an “absolute” evil.

Scientists said on Thursday that links between the Zika virus and microcephaly have been strengthened by a study involving pregnant women in Brazil.

The research confirmed the presence of Zika virus in the amniotic fluid of two women who had had Zika-like symptoms during their pregnancies.

Brazilian experts say this suggests the virus can infect the foetus. But World Health Organisation experts caution the link is not proven and expect to release more information in the next few weeks.