BEIRUT (AP) -- Zachariya Shaer's neighborhood of Beirut has been Sunni Muslim for generations. His family's roots here date to 1800 and he has documents to prove it.

Now the walls and lampposts are plastered with Shiite posters and graffiti, and in a city whose peace depends on a delicate sectarian balance, many fear trouble ahead.

Sunnis like the Shaers once predominated in the neighborhood named Zoqaq Blatt, or "tiled alley," after its French-colonial-era cobblestones. Shiites have been migrating here for decades from south Lebanon, escaping a region long neglected by the government. Their numbers have risen sharply in recent years, and Sunnis now find themselves in the minority.

The influx is paralleled by the dramatic rise of Hezbollah, the Iranian-backed Shiite militia, riding on the prestige it won in the Arab world for standing up to Israel in a 34-day war last summer. It also coincides with the ascent to power of the Shiite majority in Iraq and the feud with the Sunnis that has followed.

Accurate counts of the various Muslim and Christian groups in this nation of roughly 4 million are nonexistent. Lebanon hasn't had a census since 1932, because a sharp change in numbers could provoke calls for a change in the long-standing arrangement whereby the president must be a Maronite Catholic, the prime minister a Sunni and the speaker of parliament, the lesser of the three posts, a Shiite.

Shiites, though not a majority in Lebanon, are the largest religious group.

The tremors rolling through Lebanon began in February 2005, with the assassination of former Prime Minister Rafik Hariri, and the demonstrations that pointed blame at Syria and forced it to withdraw its forces from the country.

Next came the Israel-Hezbollah war. And in November, Hezbollah and Amal, a fellow Shiite group, quit the coalition of Prime Minister Fuad Saniora because it wanted a veto over Cabinet decisions. Since Dec. 1, the Hezbollah-led opposition has held huge rallies and a vigil in a tent city outside the government's offices in Beirut.

Many Sunnis, meanwhile, blame Hezbollah for starting a war that caused $2.8 billion worth of Israeli-inflicted damage on Lebanon.

On Jan. 25, scuffles between Sunni and Shiite college students in the Sunni neighborhood of Tarik Jdideh burst into clashes that evoked memories of the country's 15-year civil war. Cars were torched, snipers fired from balconies and roofs, and Shiite women accused Sunnis of trying to pull off their head scarves.

Beirut's Sunnis and Shiites are increasingly wary of each other.

"They want to impose their views just because they have guns," Shaer, 57, said of Shiite leaders. He said he resented the Hezbollah flags flying from an electricity pole above his appliance store, but feared his shop would be trashed if he removed them.

There are complaints of Shiite vigilantes stopping cars to check ID cards for Sunnis. Shaer's wife, Amal, says she has stopped shopping at Shiite-owned stores "after Shiites asking for her ID attacked my daughter's car."

In their neighborhood, the few banners and posters representing Sunnis, including the late Hariri and his son Saad, were torn down after the Sunni-Shiite street clashes.

In Tarik Jdideh, a couple of miles from Shiite neighborhoods, troops and armored cars have deployed following the death of a young Shiite man who was shot in December as he headed home from a protest.

Ahmed Khatib, a 27-year-old Sunni, said that when he sought to buy an apartment in Tarik Jdideh, the owner demanded assurances he was not a Shiite.

Hassan Chouman, a Shiite elder in Zoqaq Blatt, blamed the tensions on politics, not religion and said he was working to calm Sunni families.

"We visit them at their homes to assure them no harm will come to them," said Chouman, a Hezbollah member whose father moved here 70 years ago from southern Lebanon when he came to work at Beirut's port.

He said Shiite residents were nervous, too, and were increasingly asking him for ID cards that don't reveal their sect.

He said it was not Hezbollah but residents themselves who were hanging out the Shiite flags and banners. But it's unlikely any group short of an organized party could festoon every electricity pole.

The roots of the feud are ancient. Sunnis in Zoqaq Blatt say they take offense at Shiite flags with "Hussein" written on them. Hussein, later to be revered as a Shiite saint, was killed in a 7th century battle with the ruler Yazid, whom Shiites consider a Sunni.

"Provocation," Shaer said, throwing up his hands in frustration. "You either have to leave the neighborhood or stay quiet."

Shiites, for their part, complain that on the anniversary of Hariri's assassination, Sunnis chanted "Omar," the Prophet Muhammad's successor whom Shiites view as having usurped Islam's leadership.

But Shaer remembers when Sunnis and Shiites lived in harmony. His 19-year-old daughter, Hiba, said her best childhood friend is a Shiite.

Shiites started arriving in big numbers to Zoqaq Blatt during the 1975-90 civil war, moving into homes vacated by Christians and later Sunnis who fled the fighting.

Other newcomers were Shiite businessmen who had made money in Africa.

And 30 years of conflict with Israel have driven many more out of southern Lebanon in search of safety and jobs in the capital.

Even some long-term Shiite residents resent the new sectarian divisions. "Damn the day we came to Beirut," said Mohammed Ftouni, 52, a Shiite whose parents migrated from the South to Zoqaq Blatt before he was born. People in the south "are kinder despite the Israeli problem," he said.

"In this neighborhood," said a Sunni elder, "the big fish swallows the small fish." He would only be identified by his first name, Sharif, lest he get into trouble with neighbors.

By Scheherezade Faramarzi