Rallye, whose subsidiary Casino also owns top French high-street supermarket brands like Monoprix and Franprix, said late on Thursday that it had sought bankruptcy protection to reorganise its €3 billion-euro debt load.

Following trading suspensions the day earlier, Rallye shares lost over half their value on Friday morning, plunging 54 percent on the Paris stock exchange to trade at €3.50 before rebounding slightly.

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But Rallye said on Friday that Casino as well as sports chain Go Sport, which it also owns, “were not concerned” by the proceedings, which involved only the majority shareholder.

As a consequence, Casino shares surged by more than 16 percent on the Paris stock exchange to €32.52.

But since March, Casino shares are still down more than 30 percent.

Rallye, which said its debts amount to €2.9 billion, owns 51.7 percent of Casino, which is controlled through a complex holding structure by French businessman Jean-Charles Naouri. 

Rallye said that “following the persistent and massive speculative attacks” against Rallye shares, the bankruptcy protection would “ensure the integrity of the group and improve their debt profile in a stable environment.”

Shares in the group have tumbled in recent years as it became the target of short-sellers, who effectively bet the share price will fall, troubled by what analysts see as an opaque shareholder structure.

“It is key for the companies to have time to re-profile their debts within the secured framework of the safeguard proceeding,” Rallye said.

It said the safeguard proceedings would initially take six months, and potentially last as long as 18 months.