In the dim fourth-floor walk-up, past the wrestler-turned-bodyguard, the leader of the Arab European League sat in silence. Before him were a batch of newspapers bearing his image and a flier informing Belgian police that his group was "watching" them.

Last month, Dyab Abou Jahjah's group fielded unarmed patrols to follow this northern Belgian city's police officers in what the group called an attempt to prevent abuse of Arab youth. Later in the month, he was arrested and held for five days for allegedly inciting two days of riots in Antwerp that followed the fatal shooting of a young Moroccan teacher by an elderly white neighbor whom the police called deranged.

The face of Abou Jahjah, 31, has flashed across Belgian television screens often in recent months. Dressed in sharply cut suits, he gives a fresh voice to the rage felt by many Arabs in this country and across Europe. He is also forcing Belgium into a deeper conversation about whether the country welcomes immigrants and, more broadly, just who is a Belgian.

To ask those questions is to incite a fiery, complex response from the Lebanese-born Abou Jahjah, who in the days after his release remained holed up in his spartan apartment in a largely immigrant section of this port city.

"My family in the U.S. are Arab American, and they feel [American]. I'm Belgian, and I don't feel it," he said in an interview. "Belgians are unable to be multicultural, because to them, to be Belgian is to be white. So we say we're 'Arab European,' because Europe itself is multicultural and Arabs aren't new in Europe; we helped make Europe what it is today."

The 1,000 or so core members of his movement are mostly young Arab men disillusioned with Belgian society and high unemployment in their communities. White Belgians, he said in an interview, "can't look at us as equals because, in their minds, we're guests. We have to shut up and obey."

Rhetoric like this has made the country sit up and listen. There has long been anti-immigrant sentiment among many Belgians, said Badra Djait, a professor of cultural anthropology at the University of Leuven whose father emigrated to Belgium from Algeria in the 1960s. "Now, there's a real face, a real target, and it's Abou Jahjah."

One of Abou Jahjah's biggest critics is Belgium's third-largest political party, Vlaams Blok. Like maverick parties elsewhere in Europe, it is tapping sentiment that newcomers are overpowering local society and bringing a rise in street crime, and perhaps terrorism. Across the continent, these feelings appear to have grown since the Sept. 11, 2001, attacks in the United States.

"Our cities have changed into, well, Islamic neighborhoods, with mosques instead of churches, like it's some kind of Islamic state," said a spokesman for Vlaams Blok, Philippe Vander Sande. He denied the party was racist. Its point, he said, is that immigrants can "choose to assimilate with the Belgians, and if they do, they're welcome. If they don't, and say Islamic law and Islamic religion are above our Belgian law, our Western lifestyle, then we say, that's not possible. They must go."

Vlaams Blok wants Abou Jahjah to be stripped of his Belgian citizenship.

In the middle is the coalition government of Prime Minister Guy Verhofstadt. He once avoided discussing immigration, but following the Antwerp riots, he declared on Belgian television that the Arab European League is a "threat to our society" and thrives "on confrontation and provocation."

In the last two months, the group has staged two large street protests in the capital, Brussels, against U.S. aggression toward Iraq and Israeli policies toward Palestinians. In the next year, it plans to open chapters in the Netherlands and in France, which is home to about 4 million Arabs, the largest such population in Europe.

Because people of Middle Eastern descent comprise about 5 percent of Belgium's 10 million people, he has suggested that Arabic be made the country's fourth official language (Flemish, French and German are the first three) and said he might field candidates in next year's national elections.

In Antwerp, which has a sizable immigrant population, police are sent in force to break up groups of young men of Arab descent who gather on the streets; government leaders view the Muslims who shadow police patrols as illegal vigilante groups and say they frequently curse and spit on officers carrying out routine duties. Many political analysts say the national government's tough new policies are motivated at least in part by hopes of reducing support for Vlaams Blok, which controls about a third of the seats on the Antwerp city council.

Abou Jahjan was born in Beirut and said he joined the Lebaneseresistance as a teenager to fight Israel's occupation of Lebanon, and dreamed of studying at the University of Michigan, close to where his relatives live. The 1991 Persian Gulf War, he said, led him to cancel those plans, and at 19, he moved to Belgium, obtained citizenship through marriage, divorced, mastered the Flemish language and earned degrees in international politics. He is now working on a doctorate, focusing on post-Cold War security.

He observed what he considered to be Arabs being marginalized in Belgian society, and the muted response from established, government-subsidized Arab groups led by first-generation immigrants who came in the 1960s and 1970s as guest workers. "It was obvious the real problems weren't being addressed," he said of these groups, whose leaders have widely dismissed him a radical.

Antwerp remains tense. It is common to see young Arabs with hands raised leaning against storefronts, being frisked vigorously by police. Arabs say the officers often call them makukah, or "white ape"; the phrase is so familiar to youngsters , they've begun calling each other "makukah."

Abou Jahjah said that his Nov. 26 arrest, along with 160 youths allegedly involved in rioting, sent the wrong message to the Muslim community. "Some people in this organization are, shall we say, less patient than I am. So if they eliminate me, what will you have?"