MADRID - Spanish police have arrested a Colombian drug boss dubbed ‘The Mouse’, the alleged leader of a major cocaine smuggling gang accused of 400 killings, officials said on Saturday.Officers arrested the 40-year-old, whose real name is reportedly Hernan Alonso Villa, in the eastern seaside city of Alicante on Friday, according to a police statement. He is considered ‘the top leader of the military wing of the Oficina de Envigado, a Colombian criminal organisation accused of 400 killings as well as drug-trafficking, extorsion and forced displacements of Colombian citizens’, it said.‘He is one of the criminals most wanted by the Colombian authorities. He had more than 200 people under his command and was responsible for exporting cocaine to Spain, the United States and Holland,’ the statement said. Spanish officers arrested him under a Colombian extradition warrant for charges including alleged homicide and arms offences.He was carrying 40,000 euros ($54,000) in cash when he was caught, the statement said. Authorities say the ‘Oficina’ gang dates back to the 1980s when it carried out killings for the now-dismantled Medellin Cartel. Spain is one of the main entry points for illegal narcotics into Europe and Colombia is one of the world’s biggest sources of cocaine. Colombia produced 290 tonnes of cocaine in 2013, according to the United Nations Office on Drugs and Crime.