US Ambassador to Russia Jon Huntsman will boycott Russia's annual showcase economic forum in Saint Petersburg next month over the prosecution of a top American investor, the embassy said Friday.

Michael Calvey, the American co-founder of Baring Vostok equity firm, was arrested in February along with five others on fraud charges and held in pre-trial detention in Moscow. In April a court ruled to move him to house arrest.

"Mr Calvey's continued house arrest and criminal prosecution undermines efforts to create the stability needed to attract new investment and encourage more robust business interaction," Kalan said in written comments.

The Saint Petersburg Economic Forum - Russia's answer to Davos -- will take place on June 6-8.

Calvey faces charges that his equity firm defrauded Vostochny Bank of 2.5 billion rubles (USD 38.7 million). He and his firm maintain those arrested are innocent, saying the case against them was fabricated and stemmed from a shareholder dispute.

This week, a court refused to change the conditions of detention for the other foreigner charged in the case, French banker Philippe Delpal, ruling he must await trial in a Moscow jail.

Calvey had been seen as a Kremlin-friendly investor who has steered clear of politics, and his arrest has shocked Western business circles.

His multi-billion-dollar equity firm has invested in some of Russia's biggest companies including search giant Yandex and Ozon, a top online retailer.

Alexis Rodzianko, head of the American Chamber of Commerce in Russia, told AFP last month that despite Calvey's prosecution "many of our companies" planned to attend the "important" Saint Petersburg forum.

(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)