GUATEMALA CITY (AP) — Guatemalan President Otto Perez Molina has resigned in the face of a corruption scandal that has brought his government to the brink, a spokesman said early Thursday.

Spokesman Jorge Ortega said Perez Molina submitted his resignation at midnight Wednesday local time after a judge issued an order to detain him in a customs fraud case, which already has led to the jailing of his vice president and the resignation of some Cabinet ministers.

The judge's order was unprecedented, dealing the most serious blow yet to entrenched political corruption in the Central American country.

The order is not for arrest, but for Perez Molina to declare before Judge Miguel Angel Galvea, who granted the request Wednesday from Attorney General Thelma Aldana, she told Canal Antigua television.

The president will have to appear on accusations of illicit association, fraud and receiving bribe money.

Perez Molina, 64, has maintained his innocence and vows to face the legal process. No formal charges have been filed, though Aldana said there is a preliminary investigation underway into the president's possible involvement in the fraud ring.

The president's attorney, Cesar Calderon, told The Associated Press that Perez Molina will appear voluntarily as soon as they have confirmed the order was issued.

It is the first time a sitting Guatemalan president has faced prosecution, though several have faced corruption charges after leaving office.

Perez Molina is under an order not to leave the country, and on Tuesday congress lifted his immunity from prosecution.

The corruption scandal, uncovered by prosecutors and a U.N. commission probing criminal networks in Guatemala, involved a scheme known as "La Linea," or "The Line," in which businesspeople paid bribes to avoid import duties through the customs agency. The ring is believed to have defrauded the state of millions of dollars.

The scandal has already claimed the job of former Vice President Roxana Baldetti, whose former personal secretary was named as the alleged ringleader. Baldetti resigned May 8 and is currently in jail awaiting trial on accusations she took millions of dollars in bribes.

She too says she is innocent.

Protesters fill the streets almost daily over the scandal, demanding not only that Perez Molina step down but that next Sunday's presidential elections be postponed. He says delaying the vote would be against the law.

Perez Molina is constitutionally barred from seeking re-election, and whoever becomes his successor would take office in January.

Those voting against Perez Molina in Congress included members of his own ruling party.

Business leaders, Guatemala's National Council of Bishops and even the government comptrollers' office have all urged Perez Molina to step down.