The investigation began in June when the U.S. Drug Enforcement Administration told Spanish authorities about a drug trafficking gang that wanted to smuggle cocaine from South America to Spain, police said.
Spanish agents tracked two members of the ring that traveled from Venezuela to oversee delivery of the drugs.
Earlier this month, authorities seized the cocaine and arrested four people as they tried to collect it. The other four suspects were arrested in a Barcelona hotel, the police statement said without giving any dates.
Six of them are Colombian and the other two are from Venezuela, it added.
The drugs would have fetched up to euro80 million ($120 million) if peddled by street dealers, or euro45 million ($68 million) if sold wholesale, the statement said.
In another big drug bust, Spanish authorities said last week they had seized 2.5 tons of cocaine in a high-seas raid in international waters of the Atlantic on July 26 and arrested 11 people.
