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 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.

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.

“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.

Some companies are responding to the violence. 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.

Investigators search for evidence after two bombs exploded in front of the Chiron Corp. building in Emeryville, Calif., in this Aug. 28 file photo. A growing militant movement opposed to genetic engineering in agriculture and medicine is turning to violent and criminal sabotage.