WASHINGTON — Hate crimes against Muslims in the United States have soared to their highest levels since the aftermath of the Sept. 11, 2001, attacks, according to data compiled by researchers, an increase apparently fueled by terrorist attacks in the United States and abroad and by divisive language on the campaign trail.

The trend has alarmed hate crime scholars and law enforcement officials, who have documented hundreds of attacks — including arsons at mosques, assaults, shootings, and threats of violence — since the beginning of 2015.

While the most current hate crime statistics from the FBI are not expected until November, new data from researchers at California State University, San Bernardino, found that hate crimes against American Muslims were up 78 percent over the course of 2015. Attacks on those perceived as Arab rose even more sharply.

Police and media reports in recent months have indicated a continued flow of attacks, often against victims wearing traditional Muslim garb or seen as Middle Eastern.

Some scholars believe that the violent backlash against American Muslims is driven not only by the string of terrorist attacks in Europe and the United States that began early last year, but also by the political vitriol from candidates like Donald Trump, who has called for a ban on immigration by Muslims and a national registry of Muslims in the United States.

“We’re seeing these stereotypes and derogative statements become part of the political discourse,’’ said Brian Levin, director of the Center for the Study of Hate and Extremism at the San Bernardino campus. “The bottom line is we’re talking about a significant increase in these types of hate crimes.’’

He said the frequency of anti-Muslim violence appeared to have increased immediately after some of Trump’s most incendiary comments.

The latest major episode of anti-Muslim violence came last weekend, when an arsonist on a motorcycle started a fire that engulfed the Islamic Center of Fort Pierce, Fla., where Omar Mateen — the gunman in the June massacre at the Pulse nightclub in Orlando — had sometimes prayed.

Police, who called the attack “a terrible tragedy’’ for the community, arrested a local man who had criticized Islam in social media postings.

The arson, along with an earlier assault on a congregant outside the mosque and other episodes there, have left worshippers scared, said Mohammed Malik, 43, a businessman who has attended the mosque for nearly a decade.

“There is a lot of negative rhetoric,’’ he said. “The negative rhetoric is causing the hate, and in turn the hate is causing the violent acts.’’

The new study from Levin’s nonpartisan group, based on official police reports in 20 states, estimated that there were about 260 hate crimes against Muslims nationwide in 2015.

That was the most since the record 481 documented hate crimes against Muslims in 2001, when the Sept. 11 attacks set off waves of crimes targeting Muslims and Middle Easterners, Levin said. The increase last year was also the biggest annual rise since 2001, he said.

The rise came even as hate crimes against almost all other groups — including blacks, Hispanics, Jews, gays, and whites — either declined or increased only slightly, his study found. One exception was hate crimes against transgender people, which rose about 40 percent.

An advance copy of the study was provided to The New York Times.

The statistics almost certainly understate the extent of the problem, researchers say, because victims are often reluctant to report attacks for fear of inflaming community tensions, and because it is sometimes difficult for investigators to establish that religious, ethnic, or racial hatred was a cause.

In the killing last year of three Muslim students in Chapel Hill, N.C., for instance, authorities did not bring hate crime charges against a neighbor charged with murdering them, despite calls from Muslims who said there were religious overtones to the violence. Police said a parking dispute, not bigotry, was a motive.