(Adds quote, context on Ramirez)
CARACAS, Nov 29 (Reuters) - Venezuela has removed Rafael Ramirez, once a powerful oil minister and president of state oil company PDVSA, from his post as representative to the United Nations in New York, four sources with knowledge of the matter said on Wednesday.
President Nicolas Maduro this week launched an oil industry shake-up by naming a military officer to head PDVSA and promising an anti-corruption campaign to break up "mafias" that have stolen from the OPEC nation's coffers.
"He was fired last night," said a source close to Ramirez who asked not to be identified.
Two other sources said Foreign Minister Jorge Arreaza traveled to New York this week to meet with Ramirez. A separate source said Ramirez tried to fight back and negotiate but was unable to.
The Information Ministry did not immediately respond to a request for comment. Reuters was unable to immediately obtain comment from Ramirez.
Venezuela's struggling oil industry will not see an immediate impact from the removal of Ramirez, who was a close ally of late socialist leader Hugo Chavez and served as the oil czar for a decade starting in 2004.
But a brewing dispute between Maduro and Ramirez, who is believed to retain considerable influence over PDVSA, could fuel uncertainty as the company struggles under a decaying socialist economy, a massive debt burden and a possible default.
Ramirez has been openly critical of Maduro in recent weeks, writing online opinion pieces slamming the management of PDVSA for allowing oil production to plummet since he was taken off the job in 2014.
He was seen by some as angling to be a presidential candidate in next year's election. (Writing by Brian Ellsworth; Editing by Chizu Nomiyama and Jonathan Oatis)