Israeli police were yesterday looking for members of an extremist ultra-orthodox Jewish group they suspect of spray-painting virulently anti-Zionist slogans on the walls of Jerusalem's Holocaust museum.

Slogans discovered yesterday at the Yad Vashem Holocaust Memorial Centre included: "Hitler, thank you for the Holocaust", "If Hitler did not exist, the Zionists would have invented him", and "Jews, wake up, the evil Zionist regime doesn't protect us, it jeopardises us".

The overnight vandalism at Yad Vashem brought a wave of condemnation. "I am shocked by this callous expression of burning hatred against Zionists and Zionism," said Avner Shalev, the museum's director. "This is an offence to the memory of the Holocaust."

Gideon Sa'ar, the Education Minister, said: "Whoever desecrated Yad Vashem with these awful messages did it to offend the public's feelings."

Police combed the nearby Jerusalem forest from where they suspect the vandals launched their raid, while forensic experts examined the graffiti.

Some ultra-orthodox groups subscribe to the belief that the Jewish state should not be formed until the coming of the Messiah. But only a small minority condemn Israel, and a smaller one still subscribes to the conspiracy theory that Israel's founders colluded with Hitler to establish the state.

One ultra-orthodox group, Neturei Karta, has around 5,000 members but the US-based Anti-Defamation League estimates no more than 100 of these take part in anti-Israel activism, including pro-Palestinian demonstrations. The Jewish Chronicle also quoted research by the British anti-fascist organisation Searchlight, which said that a self-styled rabbi and reported Neturei Karta member had recently attended a Holocaust denial conference in Iran.

Yesterday Mordechai Hirsch, a prominent figure in Neturei Karta, told the news site Ynet: "None of our people were involved in this, but I can't comment on something I haven't seen for myself." Mr Hirsch instead sought to blame the pro-settler groups, suggesting the incident was in retribution for the evacuation and demolition of Jewish settler homes in the West Bank.

Police are convinced, however, that there is no link between the attack and the Jewish nationalistic motives behind recent incidents. These include the vandalising of a Palestinian car in the Shuafat neighbourhood of Arab East Jerusalem yesterday. The car was sprayed with the word "Ulpana" – the name of an illegal West Bank settlement which the Supreme Court has ordered to be evacuated by the end of the month.

Last week suspected settlers or their supporters sprayed racist invective on cars and slashed tyres in the mixed Israeli Jewish-Arab community of Neve Shalom. Israel's police chief, Yohanan Danino, said the attack was "especially severe" because of the community's commitment to co-existence.