It has emerged that two Russian diplomats were expelled from Spain in November on suspicion of spying.
Russia responded by expelling two Spanish diplomats last week, a Spanish foreign ministry spokesman said. 
The spokesman would not comment on reports the Russians had engaged in economic espionage. 
The spat comes before a year of high-profile cultural exchanges between the two countries.
Russia is due to celebrate a "Year of Spain" while Spain is to have a "Year of Russia".
Spain's respected newspaper El Pais said the Spanish government had not publicized its expulsions last month because it did not want to spoil the forthcoming events.