* YPF battered by reports over gov't takeover plans
* Top energy company under intense pressure for weeks
* Gov't seeks to boost output, cut fuel imports (Recasts with context, details, adds quote)
BUENOS AIRES, April 3 Shares in Argentina's biggest energy company YPF tumbled on Tuesday due to growing investor fear over a possible government plan to seize control of the oil firm.
YPF's U.S.-listed shares fell 15.5 percent to a three-year low on Monday, a holiday in Argentina, battered by weekend media reports that said President Cristina Fernandez had made up her mind on the need for the state to control YPF.
The reports said Fernandez, who has previously nationalized private pension funds and the nation's flag-carrier airline, could opt for an outright expropriation or the purchase of a stake.
YPF, which is controlled by Spanish oil major Repsol , has been under intense government pressure to boost oil and natural gas output as a surging fuel import bill erodes the country's trade surplus.
Further pressure on YPF's stock came from weekend comments by the governor of Argentina's top crude-producing province Chubut, who said he was advancing with plans to revoke YPF's concession on the key Manantiales Behr.
Six provinces, including Chubut have already stripped operating licenses from YPF, but most have been marginal in terms of overall output.
Manantiales Behr accounts for about 10 percent of the company's total national oil output and any effort to rescind the operating license would likely spark further legal action by YPF, which has accused Chubut of singling it out unfairly.
Investors in other Argentine assets have also been rankled by the government's crusade to boost flagging energy production by targeting YPF.
"The recurrent headlines for a buyout of a ... stake in YPF suggest (Fernandez's) administration remains undeterred on a policy approach of market interventionism," Siobhan Morden, head of Latin America Strategy at Jefferies & Co.
"The policy risk should continue to weigh on sentiment." (Reporting by Jorge Otaola and Helen Popper Editing by W Simon)