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 publicised its expulsions last month because it did not want to spoil the forthcoming events. BBC News
