Lisbon stocks fall sharply amid fears over fate of major Portuguese financial group

Share prices on the Lisbon stock exchange are falling more than 4 percent and Portugal's bond yields are ticking higher amid growing concern about the health of one of the country's largest financial groups.

The market turmoil was an unwelcome relapse into investor uncertainty for Portugal, which concluded its three-year international bailout program in May. Portugal needed a 78 billion-euro ($106 billion) rescue in 2011 during the eurozone's debt crisis.

Espirito Santo Financial Group suspended trading in its shares Thursday as it addressed accounting irregularities at Espirito Santo International, its largest shareholder. Espirito Santo Financial Group is, in turn, the largest shareholder in Banco Espirito Santo, Portugal's largest bank. The bank's share price fell by more than 15 percent in morning trading.

The government insists the bank is solid.