There is always a heavy police presence outside the Jewish place of worship in the Egyptian capital.
The temple, known as Shaar Hashamayim, or the Gate of Heaven, was built in 1899 and services are sometimes attended by israeli diplomats.
However, most of the country's Jewish population, which once numbered about 80,000 people, left Egypt five decades ago amid hostilities between Arab countries and Israel.
Just several dozen elderly Jews are believed to remain.
In 1979, Egypt became the first Arab state to sign a peace treaty with Israel.
Egypt has been rounding up youths with alleged links to Islamist groups over the past months, reportedly amid growing suspicions that they are being recruited to carry out attacks.
In February 2009, a bomb exploded in a busy Cairo tourist area killed a French tourist, the first deadly attack on foreigners in Egypt since bombs killed at least 23 people at a resort in the Sinai Peninsula in 2006.