PAMPLONA, Spain (AP) — More than 100 animal rights activists have called for an end to animal cruelty with a mock bull-run amid columns of red smoke on the eve of Pamplona's famed San Fermin festival.

Bull runs throughout the narrow, cobbled streets of the northern Spanish city are the main feature of the centuries-old traditional festival, which opens Friday and runs to July 14.

Activists from People for the Ethical Treatment of Animals, or PETA, and the Spanish group Animal Naturalis, dressed in black, some with bull masks made of cardboard, carrying signs reading "Stop the bloody bullfights."

Some 1 million visitors — five times the population of Pamplona — are expected for the festival. Six bulls take part in morning runs and are killed on eight consecutive afternoons in televised corridas.