Officials said Kolobov was detained in Altea Hills, a seaside development in an area on Spain’s Mediterranean coast thought to be a haven for Russian mobsters.
Kolobov was finance minister of Ukraine from February 2012 under President Viktor Yanukovych, until Yanukovych was ousted in February 2014. Kolobov has been missing since August 2014.
In January, Interpol issued a “red notice” international alert for Kolobov, along with Yanukovych and six other senior officials wanted in Kiev for alleged financial crimes.
The Telegraph reported that this was the first case of an ally of Yanukovych being seized on foreign soil.
Spain’s ABC newspaper reported that Altea Hills was an “exclusive zone” favored by “mafiosi from eastern countries”.
Kolobov is accused of colluding with senior officials to embezzle 220 million Ukrainian hryvnia (US$ 9.4 million) from the state to invest in telecoms company Ukrtelecom for private benefit.
Officials have accused Yanukovych and members of his inner circle of stealing billions during their term in government.
In February 2014, Ukraine’s new prime minister Arseniy Yatsenyuk told Parliament that after the fall of Yanukovych’s government, US$ 20 billion in gold reserves disappeared and US$ 70 billion in state funds were transferred to offshore accounts.
He also claimed that when Yanukovych fled the country, he left behind US$ 75 billion in personal debts.