Anti-monarchist demonstrations have sprung up across Spain in the wake of King Juan Carlos I's abdication announcement.
Juan Carlos has been on the throne for 39 years and was a hero to many for shepherding Spain's democratic and economic transformation.
However, his popularity big blow following royal scandals, including a 2012 elephant-shooting trip he took at the height of Spain's financial crisis during which he broke his right hip and had to be flown from Botswana to Spain aboard a private jet for medical treatment.
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Coal's share of the power mix had fallen to 7%, while wind climbed to new highs to provide 15% of the country's electricity.
State Department spokeswoman Heather Nauert said Pence "was ready to take this opportunity."
Opposition activists said government forces have brought in more reinforcements in recent days.