JACKSONVILLE, Fla. (AP) _ The National Guard, using Humvees and helicopters, began patrolling Interstate 295 on Friday to assure motorists the Jacksonville bypass is safe despite repeated sniper attacks.

The patrols started with the winter tourist season approaching and two days after the American Automobile Association and the state visitors' bureau warned motorists to avoid the highway.

''We are going to be very visible out there,'' said Sheriff Jim McMillan. ''We want to make sure that people in this community feel they're safe and the people that are visiting our state feel like they are safe.''

Gov. Lawton Chiles signed an order authorizing the state National Guard to work with the state Highway Patrol and the sheriff's office in the northern Florida city to watch the highway and overpasses.

The governor's office wanted tourists to know ''we are doing everything we can,'' said Tim Moore, commissioner of the state Department of Law Enforcement.

''These terroristic types of attacks will come to an end,'' Moore said. ''We have a public duty to keep things in bounds as much as we can and not to over alarm the public.''

Since February, at least three dozen sniper and rock-throwing attacks have resulted in one death and several injuries. The 20-mile beltway around the city's downtown area carries about 80,000 vehicles a day and is an alternate for often-congested Interstate 95.

As many as 30 guardsmen in Humvees and helicopters with infrared devices will patrol the bypass. They will not carry weapons and won't have arrest powers but can detain suspects for police, said Brig. Gen. Richard Capps, an assistant adjutant general. He gave no indication when the patrols may end.

The sheriff's office already has expended thousands of hours to solve a series of 36 confirmed crimes and 120 unverified incidents, McMillan said.

Motorists reported five shootings from moving vehicles in a four-day period in late July, 15 shootings from the roadway or overpasses, 15 rock throwings, and one combined shooting and rock attack, the sheriff said. The latest attacked was reported Oct. 30.

Investigators believe several gangs may be involved, McMillan said, listing names such as the English Estate Posse, Nation of Chaos and the Dog Jaw Posse.

The automobile association recommended that, instead of taking I-295, travelers remain on I-95, the chief highway from Maine to Florida.

It issued a similar warning in July over rock throwing by protesting Seneca Indians on the New York State Thruway.

Last year, more than 1.3 million AAA members requested detailed travel maps for the Jacksonville area. The auto club issued an advisory several months ago urging motorists to be cautious while driving on I-295 at night.

''What we're telling people now is to stay off I-295 entirely until there is a resolution to these attacks,'' AAA spokesman Tom Schroder said Thursday.

The Jacksonville Chamber of Commerce said it has received pledges of $33,000 in rewards for information leading to convictions.

The state Transportation Department said two overpasses were fenced and new lights installed as deterrents.