BANFF, Alta. - One of the most popular hiking and biking trails in Banff National Park is bringing in restrictions at the height of the summer tourist season due to fears of bear attacks.

The Lake Minnewanka Trail has been a favourite haunt for hikers and mountain bikers for decades. There are over three million visitors to the park each year and many of them take to the 32-kilometre trail northeast of the Banff townsite.

Until Sept. 15, it will be mandatory for hikers to travel in groups of at least four. At least one of the individuals will be required to carry bear spray.

"This is the first time we've required bear spray and it's only on this section of trail," Parks Canada spokesman Mark Merchant said Thursday.

"If people don't follow the rules, it gives us another thing that the law enforcement branch can fall back on. That's going to be the last recourse."

Being charged requires a mandatory court appearance where a judge can impose a fine of up to $25,000 under the National Parks Act.

Merchant said there have been no close calls this season but the risk is still there. There are an estimated 60 grizzly bears within the boundaries of the park as well as another 40 to 50 black bears. Many are now feeding on the plentiful buffalo berries in the area.

"We have had encounters in the past. We've had a mauling and we've had also just close encounters," Merchant said.

"We really need to emphasize how serious we're taking the situation on this section of trail. By telling people 'you have to carry bear spray' we really think we're going to drive that message home.

"Bear spray probably is the best tool as a last resort. It has proven more effective then firearms or anything else."

There is also a ban on mountain bikers and dogs on most of the trail.

Merchant said mountain bikers are quieter and faster than hikers and are more prone to surprise a bear. The local cycling group is supportive of the new rules, he added.

The Parks Canada website says that between 1998 and 2005 there were five bear attacks in Banff National Park in two locations: Allenby Pass near Bryant Creek and the Aylmer Pass trail near Lake Minnewanka.

All of the bear attacks were on hikers alone or in small groups and happened when they surprised female grizzlies with cubs along the trails during berry season.

There hasn't been a fatal bear attack in the park since 1980.