Israel ordered a high-priority police investigation on Sunday into anti-Christian messages scrawled in Hebrew on the walls and doors of a Jerusalem monastery, saying they marked an assault on religious harmony."Idols will be extirpated" - a line lifted from the Jewish prayer service - and "Christians Go to Hell" were among graffiti left outside the Dormition Abbey with felt-tip pens. The varying handwriting suggested several vandals had been involved.The Benedictine monastery, on Mount Zion in the Old City, is near a site where many Christians believe Jesus held the Last Supper as well as a tomb revered as the last resting place of the biblical King David and which draws many Jewish worshippers."We will not let anyone undermine religious coexistence in Israel," Internal Security Minister Gilad Erdan said in a statement, adding that police would put a high priority on "nabbing those who carried out this despicable act".Israel has been struggling with a spate of hate crimes by suspected Jewish ultra-nationalists targeting Christian sites as well as Palestinians and Israeli human rights activists.In a statement, the Latin Patriarchate of Jerusalem described the Dormition Abbey as "a significant place for interreligious dialogue between Judaism and Christianity" and voiced "hope that the perpetrators (of the vandalism) will be arrested before they put proposed threats into action".Jerusalem's Old City, which Israel captured in the 1967 war and annexed in a move not recognized abroad, has been on heightened security alert during a months-long wave of Palestinian street violence, with wall-to-wall security camera coverage and paramilitary police patrols.