Polish President Andrzej Duda has inaugurated the first museum honoring Poles who lost their lives helping Jews during WWII.

The new museum is located in Markowa, southeastof Poland, inside the renovated home of the Ulma family who were killed by German soldiers on March 24, 1944 after they were found to be offering refuge to Jews.

Jozef Ulma, his seven-month pregnant wife Wiktoria and their six young children were all executed, as were the eight Jews they had been harbouring.

"Anyone spreading anti-Semitism defiles the Ulmas' graves, and defiles the reasons why they laid down their lives: dignity, honesty, justice," President Duda said at the inauguration ceremony.

The Polish president, Israel’s ambassador to Poland Anna Azari and the descendants of Jews from Markowa who survived the Holocaust planted a tree honouring the dead on the museum's grounds.

More than 6,600 Poles -- outnumbering any other nationality -- have been honoured as "Righteous Among the Nations" by Israel's Yad Vashem institute in Jerusalem, a title given to non-Jews who stood up to the Nazis and saved Jews during WWII.

Alluding to crimes that Poles also committed against Jews during the Holocaust, Duda called for "the whole truth, sometimes distressing and appalling, because only the truth can bring a better future".

The country was shocked by revelations in 2000 that Poles rounded up and burned hundreds of their Jewish neighbours in 1941 in a barn in the northeastern village of Jedwabne.