By Andrew Cawthorne

CARACAS, March 29 (Reuters) - Venezuela has arrested a senior manager of state oil company PDVSA on suspicion of "irregularities" in contracts to supply fuel to the domestic market, authorities said on Wednesday.

The detention of international commerce manager Marco Malave, 47, followed a shakeup of personnel at PDVSA's trade department since January and amid gasoline shortages around the South American OPEC nation last week.

"PDVSA representatives denounced a series of irregularities in the protocol for contracting companies with vessels to supply the referred hydrocarbon to the Venezuelan market," the state prosecutor's office said in a statement.

The situation affected fuel distribution in seven states, including the capital Caracas, it said. Malave was arrested last week in Caracas and his bank accounts have been frozen.

President Nicolas Maduro's socialist government and Petróleos de Venezuela, S.A., familiarly known as PDVSA, have repeatedly vowed to take steps to combat corruption, which has affected Venezuela and its oil industry for decades.

Earlier this month, the heads of Venezuela-based subcontracting companies Castillo Max and Guevara Training were arrested and charged with corruption for overbilling in equipment sales at the main oil-exporting port Jose.

Jesus Osorio, the former manager of Jose terminal, was jailed in February over the purchase of two floating platforms costing $76.2 million.

Opposition leaders have said that PDVSA has been crippled by malfeasance under 18 years of socialist rule.

A probe last year by the opposition-run Congress said $11 billion had gone missing from PDVSA. The government dismissed that as part of a right-wing smear campaign.

Rumors are rife inside PDVSA and in the wider oil sector that company president Eulogio del Pino may depart soon, to be replaced by Oil Minister Nelson Martinez. There has been no official word on this. Attempts to reach Del Pino have been unsuccessful

"Del Pino's apparent replacement Nelson Martinez is part of this broader trend of promoting loyalists," Eurasia consultancy analyst Risa Grais-Targow wrote in a report on Wednesday.

"Martinez is close to Maduro, who has long wanted him to head PDVSA. Martinez represents the most viable alternative to Del Pino considering a shallow bench of skilled oil sector technocrats." (Reporting by Andrew Cawthorne; Editing by Marianna Parraga, Toni Reinhold)