* Resigning minister calls on PM Erdogan to go too
* Corruption probe pits government against judiciary
Three Turkish ministers resigned on Wednesday, a week after their sons were detained in a sweeping corruption investigation that pits Tayyip Erdogan's government against the judiciary and has rattled foreign investors.
One of those stepping down, Environment and Urbanisation Minister Erdogan Bayraktar, urged the prime minister to follow suit - an unprecedented challenge to the Turkish leader, who has cast the scandal as a foreign-orchestrated plot and purged police in response.
"For the sake of the wellbeing of this nation and country, I believe the prime minister should resign," Bayraktar, whose son was briefly detained in the case that erupted on Dec. 17, told NTV news channel.
Each of the other cabinet members who resigned, Minister Muammer Guler and Economy Minister Zafer Caglayan, has a son among the 24 people still in police custody on graft charges. They denied any wrongdoing by their sons or the government.
"I have resigned from my post of economy minister to help the truth to come out and to foil this ugly plot, which has impacted my child and my close work colleagues among others," Caglayan said in a statement.
In a separate statement, Guler called the Dec. 17 arrests "a dirty set-up against our government, party and country".
If the resignations of Caglayan and Guler were meant to help distance Erdogan from the scandal, the late timing and the public clash with Bayraktar could prove to be big hurdles.
Turkey has flourished economically during the Islamist-rooted premier's three terms, though he has been accused of authoritarianism.
With international trading on hold for Christmas, the resignations were unlikely to have a strong market impact in Turkey. The lira had plunged to an all-time low of 2.0983 against the dollar on Friday but rallied to 2.0801 on Tuesday.