Orthodox Jewish Israelis, the driving force of the West Bank settlement movement, have begun to turn their attention inward to Israel itself, moving into Arab areas of mixed cities in an attempt to cement the Jewish presence there.

Activists say that in recent years, several thousand devout Jews have pushed into rundown Arab areas of Jaffa, Lod, Ramle and Acre, hardscrabble cities divided between Jewish and Arab neighborhoods. Their arrival has threatened to disrupt fragile ethnic relations with construction of religious seminaries and housing developments marketed exclusively to Jews.

"Israel has to act as the state of its citizens," said Mohammad Darawshe, co-executive director of The Abraham Fund Initiatives, a nonprofit group that promotes co-existence between Jews and Arabs in Israel. "Ethnic preference is clearly inappropriate, violating the principles of democracy."

About 20 percent of Israel's citizens are Arabs. Most live in Arab towns and villages, with some notable exceptions, especially Haifa, the port city that is Israel's third-largest.

Before Israel's establishment in 1948, these mixed cities were populated by Arabs. Many fled or were expelled during the two-year war that followed Israel's creation. Arabs commemorate that as a "catastrophe."

The Jewish move into Arab neighborhoods for ideological reasons echoes the nationalistic fervor of the first Israeli settlers in the West Bank in the late 1960s and early 1970s. They set up trailer camps and squatted in unoccupied houses, determined to hold on to the territory for religious and security reasons.

The settler movement has grown into a huge enterprise that, with government backing, has attracted more than 300,000 Israelis into the West Bank.

While the settlements are seen as an obstacle to peace talks and considered illegal by the Palestinians and most of the international community, the current campaign is taking place inside Israel's borders.

Still, the movement of religious, nationalist Jews into the mixed cities is promoted along the same pioneering lines as the original West Bank settlements. The settlers themselves don't make the distinction between the two sides of the line, claiming it should all belong to Israel.

The Israel Land Fund, one of the organizations promoting the move, helps Jews buy property in both Israel and the West Bank with the goal of "ensuring the land of Israel stays in the hands of Jewish people forever."

Its director, Arieh King, said the fund, with the help of a donor who contributed hundreds of thousands of dollars, was instrumental in bringing about 50 families into Jaffa, a mostly Arab town that is now part of Tel Aviv. He would not identify the donor.

"There are places in Jaffa where the Islamic Movement and other groups have been radicalized," King said. "People were afraid to fly the (Israeli) national flag for fear of how the Arabs would react." Now, he said, Jews feel more comfortable there.

The Israel Land Fund is seeking investors for a $16 million residential, hotel and country club project in the northern port city of Acre, where the mostly Arab Old City has been designated by the United Nations as a World Heritage Site.

"As always, the financial rewards are outweighed by the spiritual and ideological benefit of knowing that these projects will make a huge impact in the fight to keep Acre a Jewish city," the ad for the seafront project says.

Acre, a city of about 50,000, is 72 percent Jewish and 28 percent Arab. While relations are generally quiet, Acre was convulsed by bitter ethnic fighting three years ago after an Arab citizen drove through a mostly Jewish neighborhood on the holy day of Yom Kippur, when even secular Jews keep their cars off the streets.

The efforts to bring Jews to Acre have won praise from high levels of government. Deputy Prime Minister Silvan Shalom hailed the establishment of a Jewish seminary in Acre last year a measure as "helping to strengthen the trend of Judaizing the Galilee."

"There's nothing to be ashamed of in that statement," he said at the time.

Acre's Arab deputy mayor, Adham Jamal, warned that the activists threaten to disrupt a fragile status quo.

The newcomers "don't understand the mentality of Jews and Arabs living together," said Adham, who serves under a Jewish mayor. "Those coming now aren't coming to live in Acre. They've come to kick out Arabs."

Acre's mayor, Shimon Lankri, insisted there is no policy of "Judaization," although he said he was sympathetic to a still-unapproved request to build a 100-apartment development for religious Jews in his city.

Such projects, where residents might be required to dress modestly and respect the Jewish Sabbath by not driving or blasting loud music, exist in many other communities in Israel.

"Do I have a policy that discriminates, that favors Jews? There is no such policy," Lankri said. "I myself lived in a building with Arabs and Jews for five years." He maintained that Arab and Jewish residents receive equal services in his city.

Arab activists dispute that, saying they face discrimination in Acre and other mixed cities. Arab neighborhoods are often marred by dilapidated buildings and roads, plagued by a shortage of schools and social services.

Before the religious Jews started moving into Acre several years ago, Arabs were preoccupied with the lack of equality, said Adham. With the influx of the Jewish religious nationalists, "the main subject has become Arabs and Jews, and that's dangerous," he said. "The discourse is now about demographics."

Lankri estimated that 200 religious families have moved to Acre in recent years.

A similar process is under way in Lod, about halfway between Jerusalem and Tel Aviv.

Religious Jewish activist Aharon Atias said that after he and his wife married, their "first thought" was to move to a West Bank settlement. Then they came to the conclusion that they could transplant the settlement ethos to Atias' hometown.

He undertook to reverse a Jewish flight from his blighted hometown, which is about 25 percent Arab and 75 percent Jewish, by bringing in religious Jews. His project began with two families in the late 1990s, he said.

"Now, we're an empire," Atias said. He said 400 new religious families have moved in, and six day care centers, three schools, a seminary and a pre-military academy have been built for them. Another three projects for religious Jews are under construction, with about 660 units expected to be populated within the next two years, he said.

One development is in an Arab neighborhood, and the other two are in poor, mixed neighborhoods.

"We want to prevent Arabs from becoming the majority," Atias said. "The city of Lod, since 1948, and with God's help, has been a Jewish city where non-Jews live, and it has to remain that way."

Arab activists bridle at the notion that Jews must dominate.

"They're like a cancer that enters the body and doesn't leave," said activist Horia ElSadi, a Lod native, reflecting lingering bitterness over the establishment of a Jewish state. "They want to live alone. They want Lod to be a Jewish city."