Israel on Thursday honoured the Polish couple who hid Oscar-winning director Roman Polanski from the Nazis as a child.

The late Stefania and Jan Buchala received the Yad Vashem title of "Righteous Among the Nations" for those who helped save Jews during World War II.

"Despite their very difficult economic situation, the couple agreed to take in the Jewish boy as their own son, and keep him safe," Yad Vashem said.

Their grandson accepted the medal at the ceremony in southern Poland. Polanski also attended, calling it "a very emotional moment".

The controversial film director was just six years old when Nazi Germany invaded Poland in 1939, triggering the war and forcing the family into the Krakow Ghetto.

After his father smuggled him through the barbed wire and got friends to take him in, Polanski was shuffled around, then sent to the Buchalas.

Devout Catholic peasants with three small children, they gave him shelter for nearly two years in the village of Wysoka, asking for nothing in return.

The now 87-year-old French-Polish director of "Chinatown" and "Rosemary's Baby" thanked the late couple at the ceremony, and singled out Stefania as an "exceptionally noble person".

- 'Heroic' grandparents -

Polanski had tried for years to track down the family -- to no avail. Both Buchalas died in 1953 and the village had no news of the children.

It was only in 2017 that Polanski came face to face with their grandson thanks to some detective work from the filmmakers behind "Polanski, Horowitz".

Due out next year, the documentary by Anna Kokoszka-Romer and Mateusz Kudla recounts the childhood years of Polanski and his lifelong friend and fellow Holocaust survivor, photographer Ryszard Horowitz.

Stanislaw Buchala's late father Ludwik had talked about growing up with a "brother" who moved to the US after the war. Little did he know that his childhood playmate became filmmaker Roman Polanski.

Stanislaw, who is in his 60s, told the filmmakers he was proud of his "heroic" grandparents.

"People should know, especially now during the pandemic, that a person can do something selfless for another."

In his testimony to Yad Vashem, Polanski said Stefania Buchala "provided me with shelter, risking her own life and that of her family."

The stakes were high. In occupied Poland, even offering Jews a glass of water was punishable by death.

Poland, which lost six million citizens -- half of them Jewish -- during the war, has the most "Righteous Among the Nations" of any country, at more than 7,000 individuals.

- 'For the rescuers' -

The filmmaker lives in France, as he is persona non grata in Hollywood and cannot return to the United States for fear of arrest.

Polanski pleaded guilty to unlawful sex with a minor in California in 1977, in a plea deal after he was accused of raping a 13-year-old girl. He fled the US before sentencing.

The director of Yad Vashem's Righteous Among the Nations department, Joel Zisenwine, said "the award is given to the rescuers, not the survivor".

"It is about what they did in real time, risking their lives to save a nine-year-old child," he told AFP.

"Nobody of course has any way of knowing what happens to people as adults. It has nothing to do with that."