The United States on Tuesday said it was saddened by violence in Spain amid Catalonia's referendum on independence, a vote that had been banned by Madrid.

"We were saddened by reports ... of the many people who were injured during the events over the weekend" in Catalonia, State Department spokeswoman Heather Nauert said.

"We encourage all parties to resolve their political differences nonviolently and in a way that is consistent with Spanish law," she said.

The wealthy northeastern region is home to Barcelona and boasts a distinct culture and language.

As people queued at polling stations on Sunday, riot police moved in to prevent them from voting, in some cases hitting people with batons and shooting rubber bullets, injuring over 90 people, according to regional authorities.

The Catalan government said 90 percent of the more than 2.2 million people who managed to cast their ballot voted for independence -- but over half of eligible voters did not turn out.

On Tuesday, 700,000 people -- pro- and anti-independence, young and old -- turned out for peaceful yet angry rallies in Barcelona, the Catalan capital.

It is considered Spain's worst political crisis since an attempted military coup in 1981.