The Spanish grassroots movement dubbed 15-M pitted protesters against authorities on Friday morning, when riot police cleared Barcelona's Plaza de Catalunya to make way for a cleaning crew.

When the cleaners completed their work, however, around 200 demonstrators returned to their posts without further action from the police. The early morning clash resulted in two arrests and 121 people were treated for minor injuries after riot officers used their clubs on the crowd.

Cleaners took away tents, tarpaulins, pots, signs, sleeping bags, flyers, computers and food, which protesters may claim back on Monday, the police said.

The Catalan government spokesman, Francesc Homs, defended the police operation and said its mission was exclusively to ensure passage for the cleaning crews for reasons of "safety and public order." But the opposition Catalan Socialist Party said that the commissioner of interior affairs, Felip Puig, "exceeded his authority" by ordering the charge. Puig contended that the operation aimed to guarantee "hygiene, health and safety" in the square.

The Catalan government is also wary of possible street rioting on Saturday, following the final game of the Champions League between Manchester United and Barcelona, which would be compounded by the presence of the 15-M protesters.

Meanwhile, in Madrid, where the 15-M movement began, protesters are facing increasing pressure to go home. Local business owners complain that sales have plummeted up to 70 percent due to people's fear to step into Puerta del Sol, where demonstrators have been camped out for 13 days. Business representatives also decried the sanitary problems of what they described as "a shantytown with an unbearable stench and a source of infection."

Regional authorities are demanding that the central government take action against the sit-in. Deputy Prime Minister Alfredo Pérez Rubalcaba said the executive will analyze the problem with the police and "reach a decision."