* Investigation challenges authority of PM Erdogan
* Erdogan accuses ambassadors of "provocative actions"
* Influential cleric condemns police purge
By Humeyra Pamuk and Ece Toksabay
ANKARA, Dec 21 (Reuters) - Sixteen people, including the sons of two ministers, were charged on Saturday in connection with a Turkish corruption investigation that has struck at the heart of the ruling elite and threatened the authority of Prime Minister Tayyip Erdogan.
The general manager of state-owned Halkbank was also named as one of the people charged under the action that Erdogan has called a "dirty operation" aimed at undermining his rule.
Erdogan raised the stakes in the crisis on Saturday by saying some unnamed foreign ambassadors in the country had been involved in "provocative actions". Some pro-government newspaper had accused the U.S. ambassador of encouraging the move against Halkbank - a charge denied by the embassy.
The investigation, which has roiled markets, is widely seen as a symptom of a power struggle with a U.S.-based cleric who wields influence in police and judiciary. Dozens of police chiefs have been removed from their posts since the detentions began.
That cleric, Fethullah Gulen, condemned the police purge, invoking God's punishment on those responsible.
"Those who don't see the thief but go after those trying to catch the thief, who don't see the murder but try to defame others by accusing innocent people - let God bring fire to their houses, ruin their homes, break their unities," Gulen said in a recording uploaded to one of his websites on Friday.
Erdogan has refrained from naming Gulen as the hand behind the investigation. But Gulen's Hizmet (or Service) movement has been increasingly at odds with Erdogan in recent months.
A number of Turkish newspapers close to the government on Saturday accused the U.S. Embassy for encouraging the move against Halkbank, saying the United States wanted the bank to stop its dealings with Iran.
"Get out of this country," read Yeni Safak daily's headline, with a photograph of U.S. Ambassador Francis Ricciardone.
Erdogan picked up on the allegation in a speech in the Northern city of Samsun on Saturday, saying: "These recent days, very strangely, ambassadors get involved in some provocative acts. I am calling on them from here: 'Do your job. If you leave your area of duty, this could extend into our government's area of jurisdiction. We do not have to keep you in our country.'"
The U.S. Embassy in Turkey denied any role in the investigation. "All allegations in news stories are downright lies and slander," it said in a statement.
Halkbank general manager, Suleyman Aslan, was formally arrested and charged alongside Baris Guler, the son of the interior minister, and Kaan Caglayan, the son of the economy minister, CNN Turk and others reported.
A total of 24 people have now been formally arrested and are awaiting trial on corruption allegations.
A court on Saturday ordered the release of 33 others, including the mayor of Istanbul's Fatih district, Mustafa Demir, and the son of Turkey's environment minister, the media reported.