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8 year oldIn a series of Twitter posts addressed directly to Mr Maduro, Mr Almagro also called him a "petty dictator".
Mr Maduro accused the OAS chief earlier this week of being a CIA agent and a traitor himself.
The Venezuelan president has blamed his country's economic crisis on an axis of enemy forces co-ordinated f-rom the US.
During a three-hour long news conference on Tuesday, Mr Maduro had justified his declaration of a state of emergency by saying Venezuela was under attack f-rom imperialist forces led by the CIA.
He then told journalists: "Almagro, just give up. He has been a traitor for a long time... At some point I will tell his story, I know his secrets. The Americans, the CIA, have played a master move using Almagro as their agent."
Mr Almagro, who before leading the OAS was the foreign minister of his native Uruguay, had already clashed with Mr Maduro last year after he called him "rubbish".
Mr Almagro had responded on that occasion with an eight-page open letter, saying he would be "rubbish" if he ignored the plight of the Venezuelan people.
His Twitter posts this week were both more concise and more direct.
Linking to his open letter to Mr Maduro, Mr Almagro said: @NicolasMaduro I'm not a traitor either to my ideas or my principles BUT YOU ARE A TRAITOR to your people.
In a series of 12 tweets, he also told the Venezuelan president that "you will NEVER be able to undo so much suffering, intimidation, misery and anguish you've cre-ated for your people".
"You only repeat the scripted words which your imperialist masters dictate to you".
"You will never give orders to Venezuela!"
The former president of Uruguay, Jose Mujica, has also commented on the row between Mr Almagro, who served as Mr Mujica's foreign minister, and President Maduro.
Asked what he made of the bitter exchange, he said using a popular Spanish saying that Mr Maduro was "crazy as a goat".
"They're all crazy in Venezuela, they call each other all sorts of things but they're not going to fix anything this way."
While Mr Mujica is known for his direct and outspoken manner his words are damaging to Mr Maduro, who has always praised the former left-wing president as a "comrade".
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