BERLIN/HAMBURG (REUTERS) - German police said on Tuesday (July 4) they had seized knives, baseball bats and presumed incendiary devices at locations in and around Hamburg apparently intended for anti-capitalist rioting during a Group of 20 (G-20) summit in the city on Friday and Saturday.

Authorities expect about 8,000 violent protesters to converge on Hamburg as Chancellor Angela Merkel hosts the leaders of 20 major advanced and developing economies, Interior Minister Thomas de Maiziere said on Tuesday.

Some 20,000 police will be on duty.

"There is evidence that the acts of violence around the G-20 summit that we had expected and feared will take place," said Ralf Martin Meyer, president of Hamburg's police.

Senior police officer Jan Hieber said police had probably only found a small proportion of the weapons that had been stockpiled for use in disturbances.

Police said the items found also included batons, bottles and cans presumed to be filled with flammable liquid, containers with unknown powder or chemicals, and gas masks.

De Maiziere said during a visit to Hamburg that peaceful protests were welcome and permissible in a democracy but violent demonstrators could not invoke the right to the freedom of assembly and would be suppressed.

"No demonstrator can determine whether and when and where leaders of states and governments meet in Germany upon the chancellor's invitation," he said, stressing that the summit would not be disrupted by protests.