The ceremony in Madrid's royal palace came as uncertainty persists in Catalonia, where an attempt to break away and form an independent republic has threatened the unity of Spain.
Ousted Catalan leader Carles Puigdemont on Monday vowed to form a new government despite "threats" from the central government in Madrid, after a Spanish judge refused to re-issue a European warrant for his arrest.
Catalonia heads into a 24-hour campaigning blackout Wednesday on the eve of a knife-edge vote, a potential turning point in the Spanish region's hotly disputed independence crisis.
A Supreme Court judge in Madrid began questioning separatist leaders Friday who were jailed pending a probe into their role in Catalonia's independence drive, in what they hope could signal their release.
Imprisoned former vice-president of Catalonia Oriol Junqueras and three other jailed members of his ERC party will abide by a ruling giving Madrid control over the region, their defence lawyer said on Tuesday.
A day after hundreds of thousands of people marched in Barcelona to demand the release of separatist officials, Mariano Rajoy also urged businesses not to flee the wealthy northern region.
The independence crisis in Catalonia has only made a very limited impact on the Spanish economy, EU economics commissioner Pierre Moscovici said Thursday.
The separatist party of deposed Catalan leader Carles Puigdemont, who is facing an arrest warrant issued by Spain, said Sunday that they wanted him as candidate for regional elections on December 21.
Ousted Catalan leader Carles Puigdemont called on Saturday for a united political front in the Dec. 21 election to continue the drive for independence from Spain and to protest against the imprisonment of former members of the regional government.