The shareholder group, led by O'Hara Administration Co, filed a formal complaint with the Colombian regulator, the Wall Street Journal reported. The Journal said O'Hara holds a 20 percent stake.

The shareholders claim that the offer by Catalyst benefits Pacific's co-chairmen but leaves shareholders with nothing, the Journal reported, citing sources familiar with the talks.

A committee appointed to review the offers will present its recommendations on Sunday and is expected to back the Catalyst bid, the Journal cited people as saying.

Mexican conglomerate Alfa SAB de CV earlier this week said it had not yet made a binding restructuring proposal for Pacific, saying it would inform markets if it decides to do so.

Pacific Exploration & Production, Catalyst and O'Hara all were not available for comment outside regular business hours.

(Reporting by Anet Josline Pinto in Bengaluru; Editing by Leslie Adler)