SAN FRANCISCO -- A growing militant movement opposed to genetic engineering in agriculture and medicine is turning to sabotage -- from the bombing of a biotech company to the destruction of genetically modified crops.

As a result, targeted companies are taking extra security precautions and also often altering business strategies. The violence, which the FBI says suddenly became more serious this year, stems in part from frustration that peaceful protests have failed to slow the pace of biotech's progress.

"We've seen a drastic escalation in the use of violent tactics in the past year," said Phil Celestini, head of the FBI's domestic terrorism unit in Washington.

A range of militant environmental, economic and animal-rights activist groups have used the Internet to organize around biotechnology, first in Europe and now in the United States. Many fear the technology will forever harm nature while others object to how animals are treated in drug experiments.

Wanted by FBI

A 25-year-old Californian, Daniel Andreas San Diego, is wanted by the FBI in connection with some of the most recent attacks: the bombings in August of the Bay-area biotech company Chiron Corp. and last month of a nearby cosmetics manufacturer. Aside from a few shattered windows, little damage was done to either company.

The group that claimed responsibility for the blasts, the previously unheard of Revolutionary Cells, vowed more bombings were to come.

Other anti-biotech attacks this year include the vandalism of a Chiron executive's car and the trashing of a biology lab at Louisiana State University last month.

In France, an estimated half of the 100 plots of experimental biotech crops were destroyed this year, prompting some 1,500 scientists, including two Nobel laureates, to demand an end to the vandalism.

Genetically modified crop experimentation in Britain is also in danger due to sabotage and political opposition.

"Peaceful protests aren't ending the suffering," said Danielle Matthews, a spokeswoman for Stop Huntingdon Animal Cruelty, an animal rights group that supports property destruction but not human injury. The group has waged a four-year harassment campaign to shut down the Lawrenceville, N.J., laboratory of Huntingdon Life Sciences, a company that tests drugs and chemicals on animals for companies including biotech firms.

"The companies say they care when they're faced with nonviolent protesters and then do nothing," Matthews said. "Maybe the companies will start caring when they have to pay to replace a few windows."

Almost since James Watson and Francis Crick discovered DNA 50 years ago, scientists have been exploring ways to manipulate and exploit those building blocks of life for everything from boosting crop yields to germ warfare.

But questions didn't arise about biotechnology's safety and impact on nature until San Francisco-area scientists Herb Boyer and Stanley Cohen succeeded 30 years ago in splicing genes from one species into another. Since then, opposition to biotechnology research, first in agriculture and later in medicine, has grown, especially in Europe.

Chiron spokesman John Gallagher said attacks on the company, including the alleged unauthorized use of an executive's credit card, haven't changed the way the company does business.

But there is evidence that these "direct action" campaigns are having an effect on other companies.

The accounting firm Deloitte & Touche severed its ties with Huntingdon earlier this year because of harassment of its employees. Huntingdon itself moved its headquarters from the United Kingdom to Baltimore last year because of increasing violence against it.

In Britain, Bayer CropSciences said it no longer will plant experimental plots of genetically engineered crops because the government has declined to keep the locations confidential.

Bayer was the last company carrying out such trials in the United Kingdom. Other agricultural biotech companies had previously pulled out because such experimental plots were routinely destroyed by protesters.

And the biotech company Biogemma is contemplating leaving France because its experimental crops keep getting destroyed.