Hackers stepped up attacks on a number of Israeli Web sites on Friday, including Israel’s Foreign Ministry and the municipal Web site for Tel Aviv.

The attacks are part of a broader campaign that the hacker collective Anonymous is calling #OpIsrael. The group says the attacks are in retaliation for Israeli military strikes on Hamas on Wednesday.

The campaign, which began at 3 a.m. New York time on Thursday — with coordinated attacks on several Israeli Web sites, including those of an Israeli Defense Forces blog and a private Israeli surveillance and security company — showed no signs of slowing on Friday.

By Friday, Anonymous hackers claimed to have defaced more than 600 Israeli Web sites, many belonging to private companies. They also claimed credit for taking down a Tel Aviv municipal site, tel-aviv.gov.il, and said, in Twitter posts, that they had deleted the Web databases for Israel’s Ministry of Foreign Affairs and the Bank of Jerusalem.

While the former site was still offline Friday afternoon, the latter appeared to be functioning normally.