BAGHDAD, (AP) – The number of Iraqis who have fled their homes under threat of sectarian violence has more than doubled since the start of the year, despite the increase in American troops that began in February, a humanitarian organization said.

The number of displaced Iraqis shot upward from 447,337 on Jan. 1 to 1.14 million on July 31, the Iraqi Red Crescent Organization said Saturday.

Though the addition of some 30,000 U.S. troops since February has brought down violence in Baghdad, it also led to increased clashes with militants.

“Does this surge have anything to do with it? We don’t know,” said Saeed Haqi, head of the Iraqi Red Crescent — the local partner organization of the International Committee of the Red Cross. “But they’re leaving because of the security situation in general.”

In addition to those who have fled their homes but have stayed within the country, some 2 million Iraqis have fled, with many now living as refugees in neighboring Syria and Jordan.

In its midyear assessment last month, the Geneva-based International Organization for Migration also reported a spike in internally displaced people, saying the trend started with the February 2006 bombing of a Shiite shrine in the city of Samarra, which sparked fierce sectarian fighting.

It said 63 percent of those assessed reported that they fled direct threats to life, and that more than a quarter had been forcibly displaced from their property. Ninety percent said they were targeted because of their religious identity.

Shiites have been the largest group to be displaced, representing 64 percent, with Sunnis making up 32 percent, and Christians 4 percent, the IOM said. Shiites make up about 60 percent of the population; Sunnis are about 20 percent.

Most of the people have been forced to flee their homes in Baghdad, though Haqi said all of Iraq’s 18 provinces were affected.

The IOM said broad trends suggested the displacements were leading to an even greater religious polarization of Iraq, with Shiites tending to move from the center to the south, and Sunnis tending to move from the south to the upper-center of the country. In large cities like Baghdad and Baqouba, both Sunnis and Shiites were displaced to homogeneous neighborhoods of their own sect, the IOM said.

Christians and Kurds, meanwhile, primarily fled to the northern provinces, the agency said.

“These large movements of people will have long-lasting political, social and economic impacts in Iraq and the increasingly protracted nature of displacement in the past 1 1/2 years may well be entrenching communal divisions,” the IOM warned.

“The stability that was anticipated as a result of various security plans has not materialized, and as the violence continues in Iraq, so will the displacement.”