Responding to a series of attacks in recent months, authorities decided to erect a metal fence, ban large bags, install more surveillance cameras and make visitors go through security checks to enter the festival grounds this year.

In the bloodiest incident, a German teenager fatally shot nine people at a Munich mall before killing himself. Two other attacks were carried out by asylum-seekers and claimed by the Islamic State group; several people were wounded, but only the attackers were killed.

"Personally, nothing that has happened has changed my opinion about coming to the Oktoberfest," said Nico Baunbach, a 34-year-old exhibition manager from Munich who was dressed in traditional Lederhosen, felt jacket, checkered shirt and Bavarian shoes tied to the side.

"Terrorism is in fact reducing," Baunbach said. "We're only concerned now because it looks like it's arrived in Germany."

The attacks have fed a sense of unease in Germany about the arrival of more than a million migrants since the start of last year — many of them refugees from war-torn countries such as Syria, Iraq and Afghanistan. Security officials have acknowledged that while the vast majority of migrants are law-abiding and peaceful, a small minority may be coming to Germany with criminal intent.

Still, while authorities say there is a "high abstract danger" of an attack at the 17-day festival which is expected to draw 6 million visitors, police have stressed that there's no indication of any concrete threats.

Munich police plan to have some 600 officers on hand, about 100 more than last year, during peak times. Another 450 security guards will also check bags and keep an eye on the sometimes inebriated visitors.

Despite the large attendance — up to 600,000 visitors turn up on some days — there have been few major incidents at the festival, which was first held in 1810.

In 1980 a far-right extremist set off a bomb killing 12 people and himself, and wounding more than 200.

Last year, police reported responding to 2,017 incidents, including fistfights and stolen wallets and purses. Some 20 sexual crimes were reported, including one attempted rape.

Tim Harris, who works for a pharmaceuticals company in neighboring Switzerland, said he had no second thoughts about coming to the Oktoberfest.

"I come here every year to see my friends and you can't let these things stop you doing what you like to do," said the 36-year-old. "That said, some people I work with were due to come, but because of the fence and the reported security issues they canceled."

Sebastian Schneider, a 36-year-old online marketer from Munich, blamed the lower turnout partly on the weather. After weeks of fierce sunshine the skies opened and temperatures dropped across Germany on Friday.