Berlin, Sep 17 (IANS): The Munich Oktoberfest, the world's biggest beer festival, has begun amid heightened security measures.

The beer began to flow from the first barrel after its tap was struck twice with a mallet by Munich Mayor Dieter Reiter, who inaugurated the annual festival on Saturday afternoon, reports Efe news.

According to custom, the mayor served the head of the Bavarian government, Horst Seehofer, the first litre of beer.

The 18-day Oktoberfest slated to run until October 3 is expected to be attended by some 6 million people.

A total of 600 police personnel have been deployed, while 1,600 security guards were mostly in charge of guarding the entrances and inside the tents.

Security will also be reinforced with additional high-definition spy cameras and bodycams.

The organisers have also installed a new loudspeaker system to alert visitors about any danger and to better direct the movement of crowds in case of an alarm.

The Oktoberfest is an integral part of the Bavarian culture, having been held since 1810.

In 2013, a record 7.7 million litres of beer was served at the festival.