Colombia's notorious 'Queen of Cocaine' was killed Monday, according to local news accounts, felled by motorcycle-riding gunmen who reportedly pumped two bullets though the head of Griselda Blanco.

Reports from Colombian daily El Colombiano on Tuesday indicated that Ms Blanco was assassinated while shopping in Belen, which is located northwest of Medellin, Colombia's capital.

"Ms Blanco was shot in the head while buying meat at a local store near the central square of the Belen neighbourhood in western Medellin where she had been living since after having served 20 years in a U.S. prison," another report from online Colombian news site Colombia Reports said.

Motives remain unclear on why the victim was killed decades after she departed from the illegal drug business that in the 1970s thrust Colombia into international limelight.

Local police officials in Medellin told El Colombiano that 'The Grandmother', another name attached to Ms Blanco, appeared totally retired from the illicit trade and had remained disconnected from the country's drug circles prior to her death.

Ms Blanco was tagged by U.S. authorities as the person responsible for the spread of cocaine in Florida during the late 1970s through the early 1980s, according to The Guardian News & Media.

Her drug empire, which spanned from Colombia to the south of the United States, easily made her a billionaire and a powerful figure in the underworld, U.S. anti-drug officials said.

Ms Blanco allegedly created her own drug distribution network that regularly transited cocaine into U.S. territory at the height of her group's operations.

She was pinpointed by police officials for ordering the murder of about 200 individuals, majority of which were her business rivals, though investigators have also traced her imprint on the brutal killings of a former husband and a toddler.

The Queen, media reports said, was the brain behind the assassins that delivered deaths riding on two-wheels, which ironically was the same tactic employed by her killers on Monday.

"It's some kind of poetic justice that she met an end that she delivered to so many others," Prof Bruce Bagley of the University of Miami was reported by Fairfax as saying on Wednesday.

Prof Bagley added that despite being in retirement for a numbers of years, the deadly attack on Ms Blanco was hardly surprising as "she had lingering enemies."

"Here is a woman who made a lot of enemies on her rise and was responsible for the deaths of untold numbers of people," he further explained.

Another 'accomplishment' is her mentoring of Pablo Escobar, Agence France Presse (AFP) said, who later on unleashed his own reign of drug terror when Ms Blanco was sidelined for good in the mid-1980s as U.S. authorities finally caught up with her and locked her up for murder and racketeering.

She was released and immediately deported back in Colombia in 2004.

Ms Blanco retreated in the quiet confines of Belen, Colombia's second major city, and lived a 'normal life' though neighbours, according to El Colombiano, still regarded her as "more dangerous than the devil."