Pemex said in a statement to the Spanish securities regulator that it purchased 56,377,090 million Repsol shares, or 4.62 percent, of the Spanish firm.
Repsol shares closed at 19.795 euros per share on Friday, giving the purchase a value of more than 1.1 billion euros at current market prices.
The Mexican state oil monopoly already owns 4.88 percent of Repsol and earlier this week announced plans to increase its stake in the Spanish company to 9.8 percent as part of its deal with Sacyr.
Pemex said earlier that increasing its stake in Repsol would cost about 1.2 billion euros ($1.7 billion) and that it would finance the purchase by issuing debt.
Pemex and Sacyr, Repsol’s biggest shareholder, with 20 percent, announced an alliance on Monday, saying they would vote together to increase their presence in management and on Repsol’s board.
They plan to keep their combined stake in Repsol to just below 30 percent. If they pass that threshold they would be forced to launch an offer for all of Repsol.
Sacyr issued debt to buy its Repsol stake just before its revenue from building and construction fell steeply when Spain’s housing bubble burst. It is currently renegotiating a syndicated loan of 5 billion euros it contracted at the time.
In 2009, Sacyr was in dispute with Repsol over the oil major’s decision to cut its dividend.
Argentina’s government called a board meeting at the country’s biggest energy company, YPF, to discuss the shareholder changes. Repsol controls about 58 percent of YPF.
The Planning Ministry said the meeting would allow representatives of Repsol, Pemex and Sacyr “to explain whether this ownership change will impact or alter investment or production plans ... at YPF.”
Argentine natural gas and oil production has fallen in recent years just as brisk economic growth fuels energy demand and increases pressure on the government to boost investment to guarantee future supplies.
