Bank customers in Catalonia are withdrawing symbolic amounts of money from financial institutions that have moved their official headquarters to other locations in Spain amid a political crisis over the region's independence bid.

Pro-independence umbrella group Crida Democracia called on consumers late on Thursday to put pressure on banks that made the decision. By Friday morning, dozens of people were lining up at a CaixaBank branch in central Barcelona, most of them withdrawing 150 or 160 euros from ATMs.

The amounts were closest to 155, in reference to the Spanish constitutional article with which the central government plans to revoke some of Catalonia's autonomous powers to prevent regional politicians from pushing ahead with secession.

CaixaBank and Banco Sabadell, the largest Catalan lenders, are among hundreds of financial institutions and businesses that have moved their official registration out of Catalonia.

"These banks are traitors," said Oriol Mauri, 35, owner of a children's game business in central Barcelona. "They need to see that it's lots of us who are angry."

Mauri, who withdrew 150 euros because the ATM would not allow him to take out 155, said he was not worried about businesses fleeing Catalonia.

"I'm not afraid of economic repercussions," he said. "Our power as consumers is perhaps the only way to influence and have our voice heard in Europe."

Ana Coll, a 55-year-old pharmacist who withdrew 160 euros, said peaceful street protests have not been enough to influence decision-makers in Spain and Europe.

"We need to step up our actions and do something that really hurts, and that is targeting the money," she said.

The crisis over Catalonia's quest for independence escalated on Thursday, as Spain's central government prepared for the unprecedented step of stripping the wealthy region of some of its self-governing powers after its leader refused to abandon secession.

In his latest display of brinkmanship, Catalan President Carles Puigdemont sent a letter to Spanish Prime Minister Mariano Rajoy just minutes before a deadline set by Madrid for him to backtrack on his calls to secede.

Mr Puigdemont did not give in, however, and threatened to go ahead with a unilateral proclamation of independence if the government refuses to negotiate.

Spain's government responded by calling a special Cabinet session for Saturday when it said it would set in motion Article 155 of the Spanish Constitution, which allows for central authorities to take over all or some of the powers of any of the country's 17 autonomous regions.