Oktoberfest under way amid heavy rain and tighter security

Heavy rain and stricter security did little to dampen the spirits of beer lovers at the start of this year's Oktoberfest, which opened on Saturday in the Bavarian city of Munich.

Mayor Dieter Reiter tapped the first keg at noon with a respectable two strikes to the approval of thousands of visitors gathered in one of 14 vast tents on Theresienwiese fairground.

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.

In the worst 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, checked shirt and Bavarian shoes tied to the side.

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.

While authorities say there is a "high abstract danger" of an attack at the 17-day festival which is expected to draw six million visitors, police have stressed there is 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 drunk visitors.

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 fights and stolen wallets and purses. Some 20 sexual crimes were reported, including one attempted rape.