According to acting Head of the government of Spain Pedro Sánchez, firstly, Head of Catalonia Quim Torra should condemn unrest, which led to dozens of injured.
Meanwhile, Quim Torra noted that the protests do not show the peaceful nature of the separatists' movement.
Mayor of Barcelona Ada Colau urged citizens to keep calm.
"We can not let it continue happening. Barcelona does not deserve this," she said.
Earlier, up to 12,000 people went on strike in Kyiv to influence the Ukrainian government to refuse from the Steinmeier formula.
According to the Chief of Kyiv Police Andriy Kryschenko, law enforcement officers did not record any offenses.
"No people got to the police departments and no prohibited items were seized. The order in the center of Kyiv was guarded by one and a half thousand law enforcement officers. In total, about 6000 people participated in the first protest, and in the second event which started on Independence Square and ended under the Office of the President, there were up to 12 000 participants," Kryschenko said.