In light of the current security situation in the country, and after recent events in Jerusalem's Ramat Shlomo neighborhood, the rabbis of the 'Ramat Shlomo' neighborhood in Jerusalem addressed a special letter to the residents in which the residents must call the police - even on Shabbos – if they come across an Arab or any figure that arouses their suspicion.
This is what they said:
"To the residents of our Ramat Shlomo neighborhood.
Recently there have been many non -Jewish people coming into our neighborhood, especially during the night on Shabbos and Yom Tov ... They pose a great danger to us. [Therefore] if someone encounters a person who has an Arab accent or appearance, he should not confront them, but he is obligated to call the police immediately."
The rabbis emphasize that this ruling only pertains to the residents of Ramat Shlomo and is only to be put into practice at this time (ie: it's not chas vesholom a blanket ruling to desecrate Shabbos any time they see a non-Jew on Shabbos).