Prime Minister Jan Peter Balkenende said Friday that Dutch Muslim and Jewish groups need to work together to ease tensions following a series of apparent anti-Semitic attacks.

At least four Dutch synagogues were targets of arson or stoning during Israel's three-week offensive against Hamas militants in the Gaza Strip that ended this week, and some demonstrators at anti-Israel protests shouted slogans of "Hamas, Hamas, Jews to the gas."

No one was hurt and damage has been minimal, but "the incidents are very serious," said Ronny Naftaniel of the Center for Information and Documentation on Israel.

In the latest incident, a house was torched in an Amsterdam suburb earlier this week. Neighbors said the word "Jood," or Jew, was daubed in yellow paint on the window, according to Zoomin.nl, a Dutch internet TV network, although film footage showed that part of the scrawled word was missing in the broken glass and police have not classified it as a racist act.

Balkenende met Thursday with Jewish community leaders and Friday with Muslim leaders, and said the "feelings of unease" required attention.

"I noticed last night and today that both sides expressed their willingness to work on mutual respect, on tolerance," he said after the weekly Cabinet meeting.

He said the communities need to come together to defuse hostilities. He cited as an example Muslim action last year to calm tempers after anti-Islam legislator Geert Wilders released a short film denouncing the Quran, calling it a fascist book that incites holy war.

Naftaniel has asked for tightened security around Jewish institutions, and said he conveyed the community's security concerns to the Dutch leader.

Anti-Semitic incidents, many of them employing Holocaust imagery, spiked around Europe during the Gaza offensive, according to the U.S.-based Jewish Anti-Defamation League.

But the Netherlands is particularly sensitive to anti-Semitism because of its poor record of protecting its Jewish citizens during the Nazi occupation in World War II. Of the 140,000 Jews who lived in Holland before the war, more than 100,000 were deported and murdered. About 30,000 Jews live here now.