ANKARA, Turkey — A third Turkish Cabinet minister tied to the country’s corruption probe resigned Wednesday, hours after the ministers for the economy and interior affairs both stepped down over the arrests of their sons on bribery charges.

Erdogan Bayraktar, the environment and urban planning minister, announced his resignation in an interview with the private NTV television Wednesday.

Economy Minister Zafer Caglayan and Interior Minister Muammer Guler both denied any wrongdoing as they stepped down. Their sons, along with the chief executive officer of the state-run bank Halkbank, are among 24 people who have been arrested on bribery charges.

The sweeping corruption and bribery scandal has targeted Prime Minister Recep Tayyip Erdogan’s allies, becoming one of the worst political crises during his more than 10 years in power.

Media reports said police have seized $4.5 million in cash that was stashed in shoe boxes in the home of the bank’s CEO, while more than 1 million dollars in cash was reportedly discovered in the home of Guler’s son, Baris.

Erdogan has denounced the corruption probe as a plot by foreign and Turkish forces to thwart his country’s growing prosperity and discredit his government ahead of local elections in March. His government has won three successive elections since 2002 on the strength of the relatively robust economy, a clean image and a promise to fight corruption.

Turkish commentators believe the probe is fallout from an increasingly public feud and power struggle between Erdogan’s government and an influential US-based Muslim cleric, Fethullah Gulen, whose followers are believed to have a strong foothold within Turkey’s police and judiciary. The two men, without naming each other, have been engaged in a war of words since the corruption probe was launched on Dec. 17.

As he resigned Wednesday, Caglayan again questioned the legitimacy of the investigation, which is focusing on alleged illicit money transfers to Iran and alleged bribery for construction projects.

“It is clear that the operation is a dirty conspiracy against our government, our party and our country,” he said in a brief statement. “I am leaving my position at the economy minister to spoil this ugly plot, which has involved my colleagues and my son, and to allow for the truth to be exposed.”

Guler, the interior minister, told reporters on Tuesday that he is the victim of a political plot and that there is nothing his family could not account for. He also said alleged wiretap recordings of a conversation with his son — reportedly used as evidence by police for the arrests— were tampered with, and that the cash discovered in his son’s house was money earned from the sale of a luxury villa.

The opposition had long called for the two ministers to resign, claiming their sons were taking bribes on behalf of their fathers, and insisted they should not remain in positions where they were able to influence the probe.

The government already has dismissed dozens of police officials either involved in the investigation or thought to be linked to Gulen. Journalists have been barred from entering police buildings, fuelling accusations from critics that the government is trying to impede the probe.

The investigation is one of the biggest political challenges Erdogan’s government has faced, including last summer’s nationwide anti-government protests over a development project in a beloved Istanbul park.

Copyright 2013 The Associated Press.