Police in Stamford Hill have stepped up patrols after a spate of burglaries at synagogues.
At least eight shuls have been broken into in the last two months. Small amounts of cash were taken.
Police believe the same group is behind the burglaries after two suspects were caught on CCTV.
Among buildings targeted were the Chasidey Bobov D'Ohel Naphtoli Synagogue in Egerton Road and the Zeir Agudas Israel Synagogue in Lordship Road. Others robbed have included the Satmar Beth Hamedrash Yetev Lev in Craven Walk and the Yeshivas Horomoh Beth Hamedrash in Fairholt Road.
A police source said: "We're changing our shifts and are conducting plain clothes patrols on foot around the synagogues."
Chanoch Kesselman, executive co-ordinator of the Union of Hebrew Orthodox Congregations, noted general laxity over synagogue security. "The community can help itself by being much more vigilant and security conscious.
"Those looking to steal from shuls know what the security is like and where they see there is a weakness, they will take advantage.
"We hope people will take this advice and that those responsible for opening and closing shuls for services are more aware that people can come in at any time."
Mark Gardner of the Community Security Trust said it had provided "security equipment, advice and personnel to many hundreds of communal premises in recent years. If any further assistance is needed in this situation, it goes without saying that we are here to help. It is important the criminals do not have the idea that our synagogues are easy pickings." There are 80 shuls in Stamford Hill.
Earlier this month, police in Barnet suggested a criminal with "intimate knowledge" of the Jewish community was behind a series of robberies at Golders Green shuls. Around £110,000 worth of religious items were taken in at least eight robberies. A Hackney police spokeswoman did not believe the robberies were connected.