Baden-Baden, Germany - US President Barack Obama arrived in Germany on Friday for talks with Chancellor Angela Merkel ahead of NATO's 60th anniversary summit.

The president flew in by helicopter from the French city of Strasbourg, which is jointly hosting the two-day gathering with Baden-Baden and Kehl in south-west Germany.

Before their talks, Merkel and Obama took a stroll across Baden- Baden's main square to the town hall where the president was signing the visitors book.

Strict security measures were in force for the visit, Obama's first to Germany since his inauguration as president in January.

Some 14,600 police were guarding Obama and the other 27 heads of state and government attending the NATO summit functions on the German side of the Rhine river.

German security officials were bracing for up to 25,000 anti-NATO campaigners to turn up, around 3,000 of whom have been classified as militant.

In Baden-Baden, security zones were set up around key venues, including the hotel where Merkel is staying and the building where the leaders were holding their opening dinner on Friday evening.

Manhole covers have have been welded shut and parking metres removed from city centre locations as a precaution against terrorist attacks with explosives.

Police said 500 protesters took part in an anti-NATO rally on Friday afternoon. The peaceful protest was held on the outskirts of the spa town after a court banned demonstrations in the city centre.

Protesters have registered 13 separate demonstrations in the two summit locations in Germany. They have also threatened to block roads and carry out other acts of civil disobedience.

Germany is providing 600 soldiers to help protect the summit, while NATO will deploy AWACS surveillance aircraft. Shipping along the Rhine will be halted on Saturday morning when the heads of state and government pose for photographs on a bridge linking Strasbourg to the German side. (dpa)