The main demonstration was due to kick off at 1200 GMT in the state capital Munich, around 100 kilometres (60 miles) north of the Alpine venue where Chancellor Angela Merkel is to welcome leaders from the club of rich nations from Sunday.

Environmentalists and globalisation opponents called the rally under the banner “Stop TTIP – Save the Climate – Fight Poverty”. TTIP is a proposed Transatlantic Trade and Investment Partnership that European and US negotiators are hammering out.

In Germany, Europe’s largest economy, 43 percent of people think the US-EU trade deal would be “bad” for their country, according to a recent poll, and hundreds of demonstrations against the planned pact were held across Europe in April.

Munich protest organisers said they would begin marching through the city centre at 1330 GMT and hold a final rally at 1500 GMT with between 10,000 and 30,000 participants, public broadcaster Bayerischer Rundfunk (BR) reported.

Police said 15,000 people were expected.

“We will use peaceful and creative protests to make sure our demands are heard,” Markus Weber, spokesman for an alliance of non-governmental organisations, told BR.

Merkel, who holds the Group of Seven presidency this year, will host the two-day meeting with the leaders of Britain, Canada, France, Italy, Japan and the United States amid a massive police presence.

The summit at Elmau Castle near the Austrian border is due to cover international trade, the drive toward a UN climate accord, public health, poverty reduction and global crises among other issues.

G7 opponents say the world’s top industrialised countries have repeatedly failed to take decisive action on the most pressing issues facing the world’s population.