Griselda Blanco, Colombia's infamous "queen of cocaine" of the 1970s, was murdered in the northwestern city of Medellin, police said.

Blanco, who spent two decades behind bars in the United States, was gunned down on Monday as she left a butcher shop in the western section of Medellin, the capital of Antioquia province.

The 69-year-old Blanco was shot twice in the head outside the shop in the Belen neighborhood by a hitman who sped away on a motorcycle.

She was with her pregnant daughter-in-law, who was not hurt in the shooting, police spokesmen said.

Blanco began smuggling cocaine into the United States before the rise of the Medellin cartel, led by Pablo Escobar and Carlos Lehder, and the Cali cartel, which was founded by brothers Miguel and Gilberto Rodriguez Orejuela, officials said.

Blanco came up with the idea of "exporting cocaine" to the United States and was known for not hesitating to kill anyone, including one of her husbands, who got in her way.

The drug trafficker, who was also known as "The Godmother," was a pioneer in establishing smuggling routes from Colombia into the United States.

Blanco was convicted of conspiracy to smuggle cocaine into the United States in 1985, served two decades in prison and was deported to Colombia in 2004.

The former drug trafficker kept a low profile since returning to Colombia despite once being considered one of the wealthiest women in the world. EFE