Polish anti-abortion activists have caused shock with a giant billboard poster depicting aborted foetuses and Adolf Hitler in a campaign timed to remind Poles of Nazi rule during World War Two.

"Abortion was introduced for Polish women by Hitler on March 9, 1943," reads the poster, referring to a law passed by the Nazi regime during its brutal six-year occupation of Poland.

Images of blood-red aborted foetuses are juxtaposed with Hitler's brooding face on the poster.

The anti-abortion group Pro said it was entirely legitimate to make a link between abortion and Nazi crimes.

"It is our duty to fight for the rights of murdered children," Mariusz Dzierzawski, a campaign organiser, told Reuters. "Abortion is a crime and drawing such a parallel is absolutely justified."

Separately, he told the Gazeta Wyborcza daily: "Hitler gave the right of abortion to women, including Poles, who were considered representatives of inferior races."

The poster campaign also coincides with International Women's Day on March 8, when feminists in Poland traditionally stage demonstrations to call for greater equality, including the right to an abortion.

The poster has so far only appeared in Poznan, western Poland, but Dzierzawski said Pro aimed to put it up in at least 30 other towns and cities across the country.

Abortion in staunchly Roman Catholic Poland is illegal except in a few cases. A recent survey showed more than two thirds of Poles are opposed to abortion, up slightly from 1998.

However, initial reaction to the poster was negative.

"Words fail me... Let's leave this topic to parents. They can explain the issue to their children more delicately," said Aneta Turkiewicz, a Poznan resident, as she covered her child's eyes in front of the poster.

Magdalena Sroda, a professor of ethics specialising in gender issues, said the poster was hypocritical.

"This is sick... Fascism, Stalinism... prohibited abortion, often on pain of death, so bans on abortion are strongly linked to totalitarianism," she told Gazeta Wyborcza, adding that Hitler had urged German women to reproduce as much as possible.

Using Nazi symbols and images is politically sensitive in Poland, which lost about a fifth of its population during the German occupation, many of them in death camps such as Auschwitz built by the Nazis on Polish territory.