Syahrul Yasin Limpo’s resignation comes after the agency, known as the KPK, found billions of rupiah in raids on his ministry and residence. The agency has not yet provided details of the case nor has it publicly named Syahrul a suspect.

Syahrul told reporters he had offered his resignation to the president’s office.

“The reason why I’m resigning is because of a legal process that I’m going through and have to deal with seriously,” he said, without elaborating. He urged the public to presume his innocence.

A KPK spokesman did not immediately respond to a Reuters request for comment.

The case comes amid speculation that the graft allegations against Syahrul and another former minister may be politically motivated.

In May, investigators with the attorney-general’s office arrested then-communications minister Johnny G Plate on corruption charges for his involvement in a communications tower project.

Both men are members of the National Democrats or NasDem party, which defected from President Jokowi’s coalition to back a rival in the presidential election due in February.

Having served two terms in office, Jokowi, as the incumbent is known, is not allowed to run again but his party has nominated a hugely popular candidate.

Siti Zuhro, a political analyst at the National Research and Innovation Agency, said the back-to-back cases against the NasDem politicians were suspiciously timed.

“It’s easy to draw conclusions,” she said.

But Feri Amsari, a law analyst at Andalas University, said the case against Syahrul was legitimate no matter how politicised it may be.

The KPK has denied any politicisation of Syahrul’s case.