"You can't do a thing against suicide attacks. That's why we, the Jews of Istanbul, have decided to hold our Sabbath in 10 secret locations that no one else knows about," said Silvio Ovadya, a spokesman for the Jewish community.
Two huge truck bombs were detonated outside the Beth Israel and the Neve Shalom synagogues in the heart of the city, during Saturday's day of prayers a week ago.
A total of 25 people, mostly Muslims in the street, were killed and some 300 people injured. Funerals were held on Tuesday for the six Jewish victims who included an elderly woman and her granddaughter.
The attacks, which were followed on Thursday by two more suicide attacks against the British consulate and a London-based bank, were claimed on behalf of Osama bin Laden's al-Qaeda network and a small Turkish Islamist group.
The Beth Israel and Neve Shalom synagogues were so badly damaged they will not be used for some time, but the other synagogues were closed in the wake of Thursday's second wave of bombings for fear of further attacks.
Funeral of bomb victim Yoel
"The attacks targeting the Jewish community frightened us, but we continued to pray and to go normally about our lives. But Thursday's attacks convinced us it could happen again anywhere, at anytime," Ovadya said.
"Our leaders decided that this Saturday we should meet in safe places, out of reach of suicide bombers. We hope to be able to reopen our synagogues as of next week," he added.
At the Beth Israel synagogue, a group of workers were blocking up the windows and doors of the building with bricks while police continued to patrol the area.
Mainly Muslim Turkey has a 35,000-strong Jewish community, most of them living in Istanbul. Most trace their roots back to Jews expelled from Spain five centuries ago during the Inquisition.
Since the attacks, both Muslims and Jews have sought to emphasise their long history of peaceful cohabitation, and Turkey remains Israel's only ally in the Middle East region.