The heads of the Guatemalan central bank and social security administration were arrested Wednesday on corruption charges, prosecutors said, the latest blow to embattled President Otto Perez.

Julio Suarez, the head of the Central Bank of Guatemala, and Juan de Dios Rodriguez, the president of the Guatemalan Social Security Institute (IGSS), are accused of fraud in a $14.5-million contract for dialysis services for patients covered by IGSS health insurance.

Prosecutors accuse them of bribery, influence peddling and charging illegal commissions in connection with the contract, which awarded the dialysis concession to a pharmaceutical firm called PISA last December.

Members of the IGSS board of directors and two PISA executives were also arrested.

Suarez and Rodriguez are the latest figures to fall in the Perez administration, which has also been hard hit by a separate scandal over a customs bribery ring.

Vice president Roxana Baldetti resigned this month after one of her top aides was accused of involvement in the scheme.

Perez has faced large protests calling for him to do step down.

The latest case will likely fuel the fire, as Perez had named Rodriguez to his post in 2013 with the express mission of fighting corruption at the IGSS.

A close confidante, Rodriguez had previously been the president's personal secretary.

The arrests came as thousands of indigenous Guatemalans and farmers took to the streets of Guatemala City in the latest protest demanding Perez's resignation.

"Resign brother, prison awaits you" and "Stop corruption," said some of the signs carried by protesters.

Perez said Suarez and Rodriguez had betrayed his trust as well as the country's.

"I accept part of the responsibility, because I trusted in these individuals. But that doesn't make me responsible for what they did. They defrauded the trust I placed in them," he said.

He announced he had fired the head of the presidential anti-corruption commission, Veronica Taracena, who had been named by Baldetti.